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To understand the boiling crisis mechanism, one can take advantage of the slowing down of boiling at high pressures, in the close vicinity of the liquid-vapor critical point of the given fluid. To preserve conventional bubble geometry, such experiments need to be carried out in low gravity. We report here two kinds of saturated boiling experiments. First we discuss the spatial experiments with SF$_6$ at 46$^\circ$ C. Next we address two ground-based experiments under magnetic gravity compensation with H$_2$ at 33 K. We compare both kinds of experiments and show their complementarity. The dry spots under vapor bubbles are visualized by using transparent heaters made with metal oxide films. We evidence two regimes of the dry spots growth: the regime of circular dry spots and the regime of chain coalescence of dry spots that immediately precedes the heater dryout. A recent H$_2$ experiment is shown to bridge the gap between the near-critical and low pressure boiling experiments.

Boiling crisis is a transition between nucleate and film boiling. In this communication we present a physical model of the boiling crisis based on the vapor recoil effect. Our numerical simulations of the thermally controlled bubble growth at high heat fluxes show how the bubble begins to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes the vapor spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further bubble spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. Under such conditions, we observed an increase of the apparent contact angle and spreading of the dry spot under the bubble, thus confirming our model of the boiling crisis., Comment: in French, M\'ecanique and Industries / M\'ecanique et Industries, EDP Sciences, 2004

Introducing three well-defined dimensionless numbers, we establish the link between the scale dilatation method able to estimate master (i.e. unique) singular behaviors of the one-component fluid "subclass" and the universal crossover functions recently estimated [Garrabos and Bervillier, Phys. Rev. E 74, 021113 (2006)] from the bounded results of the massive renormalization scheme applied to the...

We use the mean crossover functions [Garrabos and Bervillier, Phys Rev. E 74, 021113 (2006)] estimated from the bounded results of the Massive Renormalization scheme applied to the $\Phi_{d}^{4}(n)$ model in three dimensions ($d=3$) and scalar order parameter ($n=1$) [Bagnuls and Bervillier, Phys. Rev. E 65, 066132 (2002)], to represent the singular behavior of the isothermal compressibility of xenon along the critical isochore in the homogeneous preasymptotic domain. The validity range and the Ising nature of the crossover description are discussed in terms of a single scale factor whose value can be analytically estimated beyond the Ising-like preasymptotic domain.

The master asymptotic behavior of the usual parachor correlations, expressing surface tension $\sigma$ as a power law of the density difference $\rho_{L}-\rho_{V}$ between coexisting liquid and vapor, is analyzed for a series of pure compounds close to their liquid-vapor critical point, using only four critical parameters $(\beta_{c})^{-1}$, $\alpha_{c}$, $Z_{c}$ and $Y_{c}$, for each fluid. ... The main consequences of these theoretical estimations are discussed in the light of engineering applications and process simulations where parachor correlations constitute one of the most practical method for estimating surface tension from density and capillary rise measurements.

A new algorithm has been developed to compute low Mach Numbers supercritical fluid flows. The algorithm is applied using a finite volume method based on the SIMPLER algorithm. Its main advantages are to decrease significantly the CPU time, and the possibility for supercritical fluid flow modelisation to use other discretisation methods (such as spectral methods and/or finite differences) and other algorithms such as PISO or projection. It makes it possible to solve 3D problems within reasonable CPU time even when considering complex equations of state. The algorithm is given after first a brief description of the previously existing algorithm to solve for supercritical fluids. The side and bottom heated near critical carbon dioxide filled cavity problems are respectively solved and compared to the previously obtained results.

We report observations on very low density limit of one and two balls, vibrated in a box, showing a coherent behavior along a direction parallel to the vibration. This ball behavior causes a significant reduction of the phase space dimension of this billiard-like system. We believe this is because the lowest dissipation process along a non-ergodic orbit eliminates ball rotation and freezes transverse velocity fluctuations. From a two-ball experiment performed under low-gravity conditions, we introduce a "laser-like" ball system as a prototype of a new dynamical model for very low density granular matter at nonequilibrium steady state.

We present the master (i.e. unique) behavior of the squared capillary length - so called the Sudgen factor-, as a function of the temperature-like field along the critical isochore, asymptotically close to the gas-liquid critical point of twenty (one component) fluids. This master behavior is obtained using the scale dilatation of the relevant physical fields of the one-component fluids. The scale dilatation introduces the fluid-dependent scale factors in a manner analog with the linear relations between physical fields and scaling fields needed by the renormalization theory applied to the Ising-like universality class. The master behavior for the Sudgen factor satisfies hyperscaling and can be asymptotically fitted by the leading terms of the theoretical crossover functions for the correlation length and the susceptibility in the homogeneous domain recently obtained from massive renormalization in field theory. In the absence of corresponding estimation of the theoretical crossover functions for the interfacial tension, we define the range of the temperature-like field where the master leading power law can be practically used to predict the singular behavior of the Sudgen factor in conformity with the theoretical description provided by the massive renormalization scheme within the extended asymptotic domain of the one-component fluid "subclass".

We give simple expressions for the mean of the max and min bounds of the critical-to-classical crossover functions previously calculated [Bagnuls and Bervillier, Phys. Rev. E 65, 066132 (2002)] within the massive renormalization scheme of the F 4 d (n) model in three dimensions (d = 3) and scalar order parameter (n = 1) of the Ising-like universality class. Our main motivation is to get efficient theoretical expressions to coherently account for many measurements performed in systems where the approach to the critical point is limited but yield data which are still reproducible by the F 4 d (n) model (like in the subclass of one-component fluids).

We investigate the critical speeding up of heat equilibration by the piston effect (PE) in a nearly supercritical van der Waals (vdW) fluid confined in a homogeneous porous medium. We perform an asymptotic analysis of the averaged linearized mass, momentum and energy equations to describe the response of the medium to a boundary heat flux. While nearing the critical point (CP), we find two universal crossovers depending on porosity, intrinsic permeability and viscosity. Closer to the CP than the first crossover, a pressure gradient appears in the bulk due to viscous effects, the PE characteristic time scale stops decreasing and tends to a constant. In infinitly long samples the temperature penetration depth is larger than the diffusion one indicating that the PE in porous media is not a finite size effect as it is in pure fluids. Closer to the CP, a second cross over appears which is characterized by a pressure gradient in the thermal boundary layer (BL). Beyond this second crossover, the PE time remains constant, the expansion of the fluid in the BL drops down and the PE ultimately fades away.

From a minimal set made of four scale factors defined at the liquid-gas critical point of a pure fluid, and one adjustable parameter which accounts for particle quantum effects, we demonstrate here a master singular behavior of the correlation length for the one-component fluid subclass, using an asymptotic scale dilatation of the physical fields. Such master behavior observed within the preasymtotic domain is in conformity with the renormalized $\Phi\_{d = 3}^{4}$ Field Theory predictions at large correlation length scale of the fluctuating order parameter, for the complete universality class of the symmetrical uniaxial 3D-Ising-like systems. The following consequences are discussed: (i) A comparison between the critical state of pure fluids and the zero-temperature state leads to an intuitive analogy with the (Nerst) third law of thermo- dynamics, which authorizes specific master form for hyperscaling within the subclass of pure fluids; (ii) A master constant value of the non-dimensional critical entropy can exist for all the pure fluids at the short-ranged lengthscale of the molecular interaction. From this latter hypothesis, we show that the needed four scale factors are the four preferred directions ex- pressing complete thermodynamic (linear) continuity crossing the liquid-gas critical point on the (pressure, volume, temperature) phase surface.

We present the master (i.e. unique) behavior of the correlation length, as a function of the thermal field along the critical isochore, asymptotically close to the gas-liquid critical point of xenon, krypton, argon, helium 3, sulfur hexafluoride, carbon dioxide and heavy water. It is remarkable that this unicity extends to the correction-to-scaling terms. The critical parameter set which contains all the needed information to reveal the master behavior, is composed of four thermodynamic coordinates of the critical point and one adjustable parameter which accounts for quantum effects in the helium 3 case. We use a scale dilatation method applied to the relevant physical variables of the onecomponent fluid subclass, in analogy with the basic hypothesis of the renormalization theory. This master behavior for the correlation length satisfies hyperscaling. We finally estimate the thermal field extent, where the critical crossover of the singular thermodynamic and correlation functions deviate from the theoretical crossover function obtained from field theory., Comment: Submitted to Physical Review E

Non-universal scale transformations of the physical fields are extended to pure quantum fluids and used to calculate susceptibility, specific heat and the order parameter along the critical isochore of He3 near its liquid-vapor critical point. Within the so-called preasymptotic domain, where the Wegner expansion restricted to the first term of confluent corrections to scaling is expected valid, the results show agreement with the experimental measurements and recent predictions, either based on the minimal-substraction renormalization and the massive renormalization schemes within the $\Phi\_{d=3}^{4}(n=1)$-model, or based on the crossover parametric equation of state for Ising-like systems.

We discuss a phenomenological method which allows to determine the singular asymptotic behaviours for a pure fluid at equilibrium, when the liquid-gas critical point and the tangent plane to the characteristic surface of this point are localized experimentally, in the pressure, density and temperature coordinates., Comment: Version anglaise de l'article paru dans Journal de Physique (Paris) 46 (1985) 281-291