POSTER SESSION

ABSTRACT

Fouling is the process in which unwanted media deposited onto a surface. When underground and surface fluids, for example, are used in energy systems, calcium carbonate scale can form on contact surfaces since the fluids usually contain, among others, some dissolved calcium and carbonate ions. The scale formation on heat exchanger surfaces is a subject of great economic and technical concern to industry. Its formation produces a thermally insulated layer to impede heat transfer and to increase fluid friction, resulting in a loss of mass flow rate and operation efficiency. Currently, chemical additives are commonly used in the working fluid as a mean of mitigating scale formation. However due to increasingly stringent environmental regulations and publics concern of environment, inhibitors of future should be bio-degradable and friendly to the environment. This work presents an innovative method of developing such a new class of inhibitor through protein and genetic engineering. The new sacle inhibitor, bio-antifoulant, is bio-degradable, can be thermally regenerated and massively produced by genetic molecular technique, thus making it well suited for direct industrial applications.

ABSTRACT

We have analyzed the response of a Hodgkin-Huxley (H-H) type model-often used to simulate ccll dynamics in sino-atrial (SA) node-to single and multiple pulses of electrical stimulation. The model does not show the commonly known bi-phasic behavior for the phase response curve (PRC). Moreover, the impact of multiple pulses (overdrive suppression) is observed to last only over a single period after the train of pulses is stopped. Preliminary studies on two interacting cells show that they synchronize if conductance between cells is large.

INTRODUCTION

Much has been learned about single cells and cell aggregates from experiments. In the absence of any external perturbation, the voltage measured from the spontaneously beating cell(s) appears as shown in the first two cycles in Fig. 1 (with a constant control period or beat-to-beat interval, T₀). One type of experiment to study the dynamics of these cells involves the application of a single pulse of electrical stimulus.^1-5 A pulse of strength c₃, lasting a short fraction of the control period (c₂T₀, where 0< c₂ <1), is applied at different phases (starting at c₁T₀, measured from the last action potential); as shown in Fig. 1. Results are often presented in the form of PRCs; plotting the normalized period of the next beat T₁/T₀ (or the change in period of the next beat, T₁-T₀) as a funetion of the phase at which the stimulation was applied. Figure 1 shows the increase in the beat-to-beat interval in response to an applied current i_ext, also shown in Fig.l. Such experiments are known to show bi-phasic PRCs: the period of the beat after the applied pulse (T₁) is larger than T₀ if the pulse is applied early in the phase (case shown in Fig.1); whereas the period is smaller than T₀ if the pulse is applied late in the phase. Moreover, the measurable effect of a single pulse on the period of the beating cell usually lasts for only one period, i.e. while T₁ is different from T₀, subsequent periods T₂, T₃, etc. are close to T₀. In other (overdrive suppression) experiments, periodic trains of stimuli are applied, and the periods, after the last applied pulse, are measured.⁶ It has been found that the period of the first beat after the last applied pulse (T₁) may be significantly larger than the control period (T₀)-much larger than those that result from a single stimulus. Moreover, subsequent periods only gradually deerease to the control period (T₂>T₃>T₄...-->T₀, say over 20 beats to return within 2% of the control period).

Confidence in mathematical models for single cell or cell aggregates would grow if they displayed the experimentally observed dynamics described above. One such H-H type model was proposed by Morris and Lecar.⁷ The model has since been used in its original or modified form by researchers for simulation purposes.^8,9 It appears that this and other models of its type have not been tested for their ability to simulate the PRC, and to simulate the model's response to periodic trains of stimuli. In this paper we present the results of such a study.

MODEL AND RESULTS

We have used the Morris-Lecar (M-L) model for this study

See Refs. 7-9 for details. Parameter values are those from Ref. 8 modified to yield a control period close to l. Simulations of the set of ordinary differential equations are performed in MATLAB. Results of the single-stimulus numerical experiment for different values of the parameters, c₂ and c₃, are shown in Fig. 2. The M-L model yields T₁ > T₀ for negative c₃, and T₁<T₀ for positive c₃. Unlike the experimentally observed bi-phasic PRC, this model yields T₁>T₀ (for negative c₃) for all values of the phase, c₁.

As a second test of the model, we subjected it to a train of pulses, c₄ time units apart. Preliminary results show that for up to 20 pulses applied (with 0 < c₄ < T₀ ), T₁ is larger than T₀ as observed in experiments. However, subsequent periods, T₂, T₃, etc. are essentially indistinguishable from T₀ . Hence, the model does not adequately simulate this second important experimentally observed behavior.

Several simulation exercises have been conducted to study the dynamics of interconnected cells.^4,5,8,9 We have tested the M-L model with intercellular coupling of the form , where i_1-2 and a are the intercellular current and conductance, respectively. Results for two interacting cells show that they synchronize if the gap conductance between them is large. Results of a typical simulation with a=0.02 are shown in Fig. 3. Two cells, 1 and 2, starting from two different initial conditions, synchronize after a few cycles. The two cells no longer synchronize as a is decreased to 0.001 (not shown).

The Morris-Lecar model is being modified to accurately simulate the experimentally observed cell dynamics. Results of more extensive simulations will be presented at the conference.

REFERENCES

1. Jalife, J. et al.,"Effects of Current Flow on Pacemaker Activity of the Isolated Kitten SA Node," Am. J. Physiol, 238, H307-H316, 1980.
2. Guevara, M.R., Shrier, A. and Glass, L., "Phase Resetting of Spontaneously Beating Embryonic Ventricular Heart Cell Aggregates," Am. J. Physiol, 251, H1298-H1305; 1986.
3. Anumonwo, J.M.B., et al., "Phase Resetting and Entrainment of Pacemaker Activity in Single Sinus Node Cells," Circ. Res., 68, 138-1153, 1991.
4. Jalife, J., Ed., "Mathematical Approaches to Cardiac Arrhythmias," Annals of the New York Academy of Sciences, NY, 1990.
5. Glass, L., Hunter, P: and McCulloeh, A., Eds., Theory of Heart, Springer-Verlag, New York, 1991.
6. Wanzhen, Z., Glass, L. and Shrier, A., "Evolution of Rhythms During Periodic Stimulation of Embryonic Chick Heart Cell Aggregates," Circ. Res., 69, 1022-1033, 1991.
7. Morris, C. and Lecar, H., "Voltage Oscillations in the Barnacle Giant Muscle Fiber," Biophys. J., 35, 193-213 (1981). '
8. Somers, D. and Kopell, N; "Waves and Synchrony in Networks of Oscillators of Relaxation and Non-Relaxation Type," Physica D, 89, 169-183 (1995).
9. Endresen, L.P., "Chaos in Weakly-Coupled Pacemaker Cells," J. Theor. Biol. 184, 41-50 ( 1997).

ABSTRACT

Problems which involve a phase change have received enormous attention in recent years. We present in our study an experimental phase change results in porous media and bounded domain. The intrusion of measurement apparatus perturb and modify the problem. In order to have an exact experimental solution in porous media where observation is impossible we develop an acoustic method. The medium used experimentally to modelize the porous medium is a stacking glass spheres whose diameters are fixed and large compared with the ultrasonic wavelength and whose spaces are filled with water (or ice). Because of spheres induced speckle, the water-ice interface cannot be seen a priori. In order to evidence this interface we have used a method based on correlation similar to the short time Fourier analysis. The result thus obtained shows that the water-ice interface can then be seen clearly.

INTRODUCTION

Problems which involve a phase change have received enormous attention in recent years [1-5]. The main feature of such problems is the moving interface at which, the phase change occurs. Unfortunately, exact solutions are available only for a few number of simplified problems. Therefore, numerical methods appear to be the only practical methods to handle phase change problems the follow of moving interface. But numerical model can not be used if no validation with experimental results is done.

For a problem where the observation is impossible (porous media) we develop an acoustic method in order to have an exact experimental solution in porous media. This technic can also be used in medical field (cryosurgery) where the media is opaque.

First experimental set up is presented then the principle of the short time correlation analysis is illustrated.

EXPERIMENTAL SET UP

The experimental set up is presented on figure 1. The porous medium is made of spherical glass balls (diameters = 1cm) placed side by side put inside ice or water. The ultrasound is generated by a plane transducer Panametrics. Its central frequency is 2.25 or 5MHz. It is excited by a 300 volts short pulse from a Panametrics generator (ref. PR502). A numerical scope Tektronics records the reception signal and then the information is stored and processed with a PC computer.

PRINCIPLE OF THE DETECTION

In this part, we present the principle of the algorithm used to detect an moving interface. Because of the balls, the ultrasonic wave in the medium is not coherent anymore. The balls induce constructive or destructive interferences like the speckle in B ultrasonic imaging [6]. The detection of the interface position becomes difficult, if not impossible. The detection is not improved by the averaging of several A lines because of the interferences are determinist. An A line can be split into two parts called part (1) and part (2) and corresponding to the target signal located after (1) and before (2) the water-ice interface. With the modification of the front position, only the speckle due to the targets situated after the interface is modify.

To detect the position of this interface a possible solution is to match two consecutive lines and so to split the two parts of the lines. An adapted operator is the correlation coefficient d [7]. We must use some points defining a window to calculate one value of this coefficient. In order to cover the depth we calculate different values of d by shifting this window along the A line. This treatment is called "short time correlation analysis".

Figure 2 shows the simulated echographic signal (A line) with phase difference after 250 points. The short time correlation shows the temporal position of the signal change. This simulated case illustrate the sensitivity of the algorithm to detect little change in the signal.

EXPERIMENTAL RESULTS

We propose to follow the evolution of the front of freezing inside the porous medium and to compare the experimental results obtained by the short time correlation analysis to the results calculated by a semi analytic method. The echographic signal is sampled with 5000 points. The period sampling is 20ns. We store one A line each 120 seconds in a PC. The cross correlation of the two lines is calculated in a one hundred points sliding. Because of ice and water have different densities, the balls move during the freezing (or the unfreezing), and consequently the correlation is locally modified. For the latter reason we have selected a detection threshold to fix the position of the phase change interface such as 1-d(t) = 0.3 All the points corresponding to the position detected with this criterion are fitted by the expression .

This experimental result must be compared with the Stéfan's analytical solution established for a phase change in a unidimensionnal domain. The corresponding position of the phase change is given by equation , where x is the distance between the exchanger and the interface, t is time, a is equivalent thermal diffusivity and l is a factor resulting from a numerical resolution [9].

In our case the experimental conditions give , this value is to be compared with 0.82 which is obtained with short time correlation analysis algorithm. Nevertheless a difference exists in the square root expression, due to the time of about 1 mn needed to install the set-up constituents (porous media, exchanger, acquisition system). The other difference is a 3 cm translation introduced by the non detection at the initial time of the phase change interface, which corresponds to the exchanger position. In order to avoid this problem the transducer can be implemented inside the exchanger in a future experimental set up.

CONCLUSION

The aim of this paper in perfecting the algorithm which allows the detection of the moving interface position inside a medium with high speckle. We demonstrate the pertinence of the local correlation analysis in the case of the time follow of the ice-water interface in porous medium.

The future objective is to use this experimental procedure in order to validate numerical results of different phase change models in a porous medium.

REFERENCES

• G. Gioda, L. Locatelli F. Gallavresi, " A numerical and experimental study of the artificial freezing of sand", Can. Geothech. J. ,31, 1-11, 1994.
• W. Z. Cao, D. Poulikakos, " Transient solidification of binary mixture in an inclined rectangular cavity ", Journal of Thermophysics and Heat Transfer, 6, n 2, 326-332, 1992.
• Konrad.J.M., 1992 : Analyse numérique des chaussées soumises à l'action du gel, du dégel et du trafic routiers., Actes du colloque organisé par l'école nationale des ponts et chaussées, Paris.
• P. Leclaire, 1992 : "Propagation acoustique dans les milieux poreux soumis au gel - Modélisation et expérience", Thése de Doctorat, Université Paris 7.
• D. Gobin, C. Benard, 1992 : Melting of metals driven by natural convection in the melt: influence of Prandtl and Rayleigh numbers. Journal of Heat Transfer, 114, 521-524.
• R.F. Wagner ; "Statistics of speckle in ultrasound B-scans ", IEEE Trans. on Ultrason., US30, 3, P156-163, 1983.
• J. Max ; "Méthode et techniques de traitement du signal et applications aux mesures physiques " Ed. Dunod, Paris France, 1987.
• H. S. Carslaw, J. C. Jaeger, "Conduction of Heats in Solids", Oxford University Press, 282- 296, 1959.
• M. Benzadi, R. Duval, R. Bennacer, H. Beji, "An analytical model for some change phase problems in bounded domains compared with numerical and experimental results. Symposium on Advances in Computational Heat Transfert, (Cesme-Turquie, Mai 1997).

† Department of Surgery and ††Department Geophysical Sciences, University of Chicago; and ‡ Rush Medical College

ABSTRACT

Electrical arcs occur in over 70% of electrical injury incidents. Historically "curable burn" distances from an energized surface along with personal barrier protection have been employee safety strategies used to minimize electrical hazard exposures. Here the 2- dimensional computational simulation of an electrical arc explosion is reported using color graphics to depict the acoustic force propagation across the geometry of a hypothetical workroom. The theoretical results are compared to the experimental findings of a staged electrical arc involving a mannequin worker monitored for electrical current flow, temperature and pressure. This report demonstrates a credible link between electrical explosions and possible pressure (acoustic) wave trauma at positions which would be considered "safe". Our ultimate goal is to protect workers through the design and implementation of preventive strategies that properly account for all electrical arc-induced hazards, including electrical, thermal and acoustic effects.

BACKGROUND

Electrical arcs are often accompanied by significant thermal energy release and explosion. However blast trauma may not be readily appreciated in survivor triage because of the sub-second time course of these scenarios and the absence of significant external wounds. Baro-trauma leading to brain injury, tissue damage at air-fluid boundaries internally (e.g., lungs, ears, bowel) as well as concussions from explosion shrapnel may not be accompanied by electrical contact sites or burns. Present practices and work rules are primarily designed to be protective of electrical and thermal exposures. Only recently have design and work policy modifications been entertained around modulating the acoustic effects of electrical incidents.

METHOD

Acoustic force propagation: A room of dimension 10 m² was postulated to have a 9 m center wall of 1 m thickness down the middle. (Such a configuration illustrates a typical set up in an electrical work space.) A blast with an energy of 20 kJ per 4 m arc length was postulated initially concentrated in a 10 cm-cylinder, then propagated through the room space.

Temperature history: A staged electrical arc fault in a 480 V/ 22,600 amp equipment setup including a mannequin worker with a measured pressure wave of 2160 lbs/ft² and 141.5 db sound (Jones et al, IEEE Paper No. PCIC-97-34, 1997) was videotaped using high-speed color 16 mm photography (Photec IV camera no. PSI-164-8-115, serial #317) at 10⁶ frames/s for 1.5 s. The film was digitized. Frame capture was done as illustrated in Fig. 1 from the test sequence. For temperature history, thermocouples (Type T) connected to an Astromed GE Dash-10 recorder were placed at the worker's extended hand (T1), neck (T2) and chest (T3) under clothing.

RESULTS

Graphical display of the 2D computational modeling of the acoustic wave propagation is illustrated. Pressures modeled at the boundaries of the wave range from -2 psi to + 3 psi and are captured in 5 ms increments. The temperature history from the staged experiment showed at T1 peak >225^oC with 90% rise in 10 ms and 90% fall in 2000 ms; T2 peak >225^oC with 90% rise in 120 ms and T3 peak 50^oC with 90% rise time at 230 ms in similar electrical arc conditions.

DISCUSSION

Bureau of Labor Statistics US data for 1994 show 11,153 cases of reported days away from work due to electrical burns, electrocution/electrical shock injuries, and fires and explosions. Electrical arc scenarios can create destructive air pressure waves due to the subsecond thermal expansion of air. Here we demonstrate the influence of the geometry of a hypothetical work area on the propagation and theoretical magnitude of an acoustic force generated under conditions similar to staged arc tests. The theoretical pressures calculated with the 2D modeling are consistent with the measured pressures in a staged test. For survivors, the blast effects of electrical arcs experienced are independent of direct electrical and thermal trauma. For purposes of engineering design and employee education and training, the illustration of acoustic wave propagation shows that near proximity to an electric arc initiation is not necessary to experience significant pressure effects from these incidents. For triage settings, this report supports the recommendation of a high degree of clinical suspicion of baro-trauma subsequent to electrical arc exposure. In the workplace, protective measures are warranted (for example, investment in arc resistant switchgear in industrial applications or use of dampening surface treatments in electrical areas) to address potential blast exposures in addition to electrical and thermal hazards of electrical arcs.

ACKNOWLEDGMENT

The staged electrical arc test and estimates of acceleration were supported in part by the Amoco Foundation. Computational analysis and 2D simulation of acoustic force propagation was supported by a 1997 University of Chicago Department of Surgery Interdepartmental Collaboration Starter Grant. Dr. Capelli-Schellpfeffer's research commitment is also supported by the Electric Power Research Institute (Palo Alto, CA; Dr. Raphael C. Lee, PI).

FIGURE 1

¹ Laboratoire d'Etudes Thermiques, (UMR-CNRS 6608), ENSMA BP 109, 86960 Futuroscope cedex, France
² Laboratoire d'Etudes Thermiques, (UMR-CNRS 6608), ESIP 40, av. Recteur Pineau, 86022 Poitiers, France
³ Service de Pediatrie du Centre Hospitalier Universitaire, CHU 350, av. Jacques-Coeur, 86021 Poitiers, France

Keywords : infant bedding - sudden infant death - thermal plume - heat transfer.

INTRODUCTION

Recommendation for supine position was followed by an efficient improvement in sudden infant death syndrome (SIDS), but no explanation is given for the association between SIDS and prone position, nor for its decrease in supine. Nevertheless, hyperthermia is thought to be the main factor related to SIDS. Normally, the mechanisms of heat and mass transfer (evaporation, convection, conduction and radiation) are more than enough to transfer the metabolic heat produced by the body. However, when the body insulation increases (clothes, blanket), overheating may appear and should be transferred by the head, whose heat clearance efficiency can greatly vary with environmental configurations.

The purpose of the present study is to quantify the influence on natural convection heat transfer around the head of :

• - the modification of the thermal plume over the head in selected cases in which the infant is sleeping prone, and access to fresh air reduced by bedding,
• - the embedding of the head in the mattress,
• - the reinforcement of the thermal plume over the head due to mattress heating by conduction.

EXPERIMENTAL STUDY

As an introduction of this paper, we first present some experimental results concerning the influence of the position of the infant. This study was achieved in collaboration with the Paediatric Department of the Hospital of Poitiers. We selected infants presenting pathology that permitted prone and supine position. Thermocouples were placed both on the skin and in the close environment of the infant and temperatures were recorded in prone and in supine position. Actually, changing from supine to prone position induces :

• - an increase of temporal temperature (1.1°C) and frontal temperature (0.5°C), whereas trunk skin temperature remains stable,
• - an increase of head plume aerial temperature (1.5°C) and neck aerial temperatures (0.3/0.5°C), whereas trunk plume aerial temperature remains stable.

It clearly reveals overheatings due to the position and we could also identify such an overheating due to local confinement effect near the head.

So, we decided to focus on the head and improve our understanding of mechanisms which could reduce heat clearance efficiency of that body part. We have then performed computational evaluation of heat transfer around a simplified representation of the infant's head.

INFLUENCE OF EXPIRATED HEAT UNDER PARTICULAR BLANKET CIRCUMSTANCES INDUCING A CONFINEMENT EFFECT

When an infant is laid prone, there are possible cases where the access to fresh air is reduced by bedding. A particular case of interest is when the blanket takes the shape of an open cavity where infant breathes (fig 1,2). A computational fluid dynamic (CFD) code was used to quantify the influence of expirated heat in those circumstances (fig 3). We considered for this a sphere, representing the head of a 6 month old infant, slightly embedded (j_o=157.5°, fig 3) in a mattress of known conductivity. We also used a more conventional analytical approach named integral method.

When the cavity is placed in the expiration axis, the heat transfer coefficient decreases, down to 10% less than the corresponding value without the cavity. Assuming heat/mass transfer analogy of Colburn, this can represent a decrease of about 0.6 W of heat clearance capability (about 7 W are evacuated by the head).

EFFECT OF EMBEDDING

When the infant is laid down, his head slightly embeds in the mattress, depending on the mattress material density, and a thermal plume develops (fig 4). We first calculate mean heat transfer coefficients as a function of embedding, assuming that dynamic and thermal boundary layers are developing from the intersection of the sphere and the mattress. Characterising the embedding with the angle j_o , we assumed a realistic variation of j_o from 135° to 169° (fig 5), and performed a sensitivity study relatively to this parameter.

Between these two extreme angles of embedding, the decrease of heat transfer surface area and the modification of the dynamics of the flow induce a decrease of about 25% of convective heat transfer. If we consider sensible and latent losses, assuming Colburn's analogy, it represents a decrease of 1,5 W of heat clearance capability.

INFLUENCE OF THE CONDUCTION IN THE MATTRESS

In order to quantify the influence of conduction trough the mattress on the convective plume over the head, we have let the dynamic and thermal boundary layers start on the mattress itself (fig 6). We have characterised the diffusive contribution in the mattress by the length L.

For L=0, we retrieve mean heat transfer coefficients very close to that calculated previously.

As L rises up to one radius of the sphere increasing starting length of the plume, it induces a decrease of corrected mean heat transfer coefficients with a fall of 30%. If we cumulate the effect of embedding and the effect of increasing starting length, it implies a decrease of about 45% of heat clearance capability which represents 2.7 W.

CONCLUSION

The thermal plume of natural convection around the head is greatly influenced by bedding confinement effects, mattress conductivity, and mattress density. The cumulative effect of these parameters on heat loss capability can reach 50% of decrease. To the infant point, it could eventually be more than enough to be quickly lethal.

ACKNOWLEDGEMENTS

The present study was supported by grants from the Region Poitou-Charentes.

ABSTRACT

In this paper, we studied solution of inverse heat conduction problems. Unfortunately ,such problems are also ill-posed. But the transient heat conduction equaüon can be either linear or nonlinear. For the linear case the partial differential equation formulation can be equivalently presented by an integral equation. First kind Voltera integral equation problems arise in the family of problems.

Recently, classical methods were described based on predictor-corrector ,Tikhonov regularization methods. But, we studied the solutions of Voltera integral equation with convolution kernel by the preconditioned conjugate gradient method. Moreover, our aim is to given an easy and general scheme of constructing good Circulent integral operators as preconditioners for such equations. Numerical examples are also given.

ABSTRACT

Fluid management in hygiene products, such as baby diapers, feminine hygiene pads or adult incontinence diapers is a very complex process which requires an efficient interaction of the various components of the hygiene product, especially of the so called "pad" of the hygiene product.

This pad consists of fluff fibres from fluff pulp, which differs from ordinary paper pulp manufacture in the drying and converting steps, superabsorbent polymers (SAP), which are to a large extent synthetic polymers consisting of slightly crosslinked, partly neutralised polyacrylic acid, nonwoven cover sheet and transition layers, which consists of voluminous and lofty nonwoven or a crosslinked fluff pulp.

A hygiene product has to have very good absorbency, this refers to efficient take up of urine and faecal material or blood. This also means no resulting leakage from the sides of the hygiene product. Furthermore requirements are avoiding wetness on the skin and a good skin care.

The pad's first task is to provide a proper fluid acquisition. This can only be managed if the pad has also the ability to properly distribute the fluid in order to make the necessary pore volume in the structure available. After fluid acquisition and distribution the SAP absorbs the fluid from the pores of the fibrous pad.

The transition layer has to be able to pick up the body fluid from the nonwoven cover sheet very fast and distribute it to the absorbent core which consists of fluff fibres and SAP, which is either randomly distributed in a fluff fibre matrix or placed in layers. Therefore the specific functions of the transition layer are good wicking and fluid transporting properties.

The fluff fibres estimates generally the fluid transport within the core and the core strength. Also there is a small contribution to the absorbency, but the most part of the absorption and the storage of the body fluid is done by the SAP. They are capable of absorbing and retaining large quantities of body fluids, even under pressure.

The body fluid is supplied at a specific rate and volume which depends on the nature of the application and on the size of the person wearing the hygiene product. Also it's time staying within the hygiene product and it's transport through the hygiene product is very varying. Furthermore it is possible that the body fluid solves substances, which lead to a skin irritation.

Especially most clinical and laboratory studies have shown that increased wetness, increased skin pH and the mixing of urine with faeces are the prime factors in diaper dermatitis which is a common affection for many babies.

Therefore it is necessary also to investigate the fluid transport within the hygiene product and the body fluid after transport through the hygiene product. This "padfluid" has an influence of the temporal growth of Tetrahymena pyriformis, which are sensitive to histotoxic noxae that is generally similar to that of human and animal cellular tissue cultures.

The transport processes are investigated and will be discussed with vertical and horizontal fluid distribution conductivity experiments, vertical absorption and retention under pressure and surface wetness experiments.