Condensation Shock Wave Research Articles

Effect of Humidity on Transonic Flow

An experimental investigation of the effects of humidity-induced condensation on shock/boundary-layer interaction has been conducted in a transonic wind-tunnel test. The test geometry considered was a wall-mounted bump model inserted in the test section of the wind tunnel. The formation of a lambda-shape condensation shock wave was shown from schlieren visualization and resulted in a forward movement of the shock wave, reduced shock wave strength, and reduced separation. Empirical correlations of the shock wave strength and humidity/dew point temperature were established. For humidity levels below 0.15 or a dew point temperature of 268 K, the effect of humidity was negligible. The unsteady pressure measurements showed that if a condensation shock wave formed and interacted with a main shock wave, the flow becomes unsteady with periodic flow oscillations occurring at 720 Hz.

Study on Operational Characteristics of Supersonic Steam Injector

The supersonic steam injector, one of the innovative technologies has been developed as a candidate of the most important component for next-generation nuclear reactors. The supersonic steam injector has functions of a passive pump without a large motor or turbo-machinery and a high efficiency heat exchanger. The performances of the supersonic steam injector as a pump and heat exchanger are dependent on direct contact condensation phenomena between a supersonic steam and a subcooled water jet. In the present study, the supersonic steam injector, which is made of visible transparent material and equiped with the measurement instrumentations for both axial/vertical temperature and velocity, is used to obtain the axial pressure distributions, the spatial temperature and velocity distributions in the supersonic steam injector. The visual observation on the interface of a water jet steam was made by a high-speed movie. The observation results reveal that there exist the condensation shock wave at the throat, the water jet surface fluctuation, and that the entrainment occurs on the water jet surface. The radial temperature and velocity distributions exhibit that the temperature and the velocity in the water jet are mostly symmetrical and higher at the downstream.

Analysis of Nitrogen and Steam Injection in a Porous Medium with Water

We formulate conservation laws governing steam and nitrogen injection in a one-dimensional porous medium containing water. Compressibility, heat conductivity and capillarity are neglected. We study the condensation front and shock waves arising in the flow. We find that there are four possible types of solutions for the initial and boundary conditions of interest. We describe a simple construction in the temperature saturation plane that determines the complete solution for the given conditions. Applications of the theory developed here are in clean up of soil contaminated with nonaqueous phase liquids. We show that a substantial cold gaseous zone develops in all solutions of practical interest, thus counteracting downward migration of the pollutant.

2631 超音速蒸気流中の水噴流挙動に関する研究(S57-2 原子炉システムおよびその要素技術(2),S57 原子炉システムおよびその要素技術)

Next-generation nuclear reactor systems have been under development aiming at simplified system and improvement of safety and credibility. One of the innovative technologies is the supersonic steam injector, which has been investigated as one of the most important component of the next-generation nuclear reactor. The steam injector has functions of a passive pump without large motor or turbo-machinery and a high efficiency heat exchanger. The performances of the supersonic steam injector as a pump and a heat exchanger are dependent on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. In previous studies of the steam injector, there are studies about the operating characteristics of steam injector and about the direct contact condensation between static water pool and steam in atmosphere. However, there is a little study about the turbulent heat transfer and flow behavior under the great shear stress. The present study, visible transparent supersonic steam injector is used to obtain the axial pressure distributions in the supersonic steam injector, as well as high speed visual observation of water jet and steam interface. The experimental results of the interfacial flow behavior between steam and water jet are obtained. It is experimentally clarified that an entrainment exists on the water jet surface. It is also suggested that the condensation shock wave causes the rapid pressure increase.

Study of moist air flow through the ludwieg tube

The time-dependent behavior of unsteady condensation of moist air through the Ludwieg tube is investigated by using a computational fluid dynamics (CFD) work. The two­dimensional, compressible, N avier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin- Lomax turbulence model is employed to close the governing equations. The predicted results are compared with the previous experiments using the Ludwieg tube with a diaphragm downstream. The present computations represent the experimental flows well. The time-dependent unsteady condensation charac­teristics are discussed based upon the present predicted results. The results obtained clearly show that for an initial relative humidity below 30% there is no periodic oscillation of the condensation shock wave, but for an initial relative humidity over 40% the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to unsteady condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity and it results from the periodic excursions of the condensation shock wave.

Passive control of condensation shock wave in Prandtl-Meyer expansion flow

In this paper, the effects of the passive technique by using the slotted wall on the characteristics of a condensation shock wave generated in a Prandtl-Meyer flow were investigated experimentally. Furthermore, in order to clarify the variation of condensation properties in the flow field, Navier-Stokes equations were solved numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second-order fractional-step for time integration. Baldwin-Lomax model was used as a turbulence model in the computations. From experimental results, it was found that the shock strength on the slotted wall became weak in comparison with no passive case (solid wall), and the present passive technique was the most effective when a foot of the condensation shock wave was located at the middle of slotted wall. Furthermore, it was confirmed numerically that the passive technique was also effective for the unsteady condensation shock wave.

Effect of Non-equilibrium Condensation of Moist Air on Flow Fields in a Ludwieg Tube(Case without Condensation Upstream of Nozzle)

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to non-equilibrium condensation. If the latent heat released by condensation exceeds a certain quanity, the flow becomes unstable and a periodic flow oscillation occurs. In the present study, a numerical study of moist air flows in a supersonic nozzle was carried out using a special short duration supersomic wind tunnel, called a Ludwieg tube. The effect of the initial relative humidity of the moist air on static pressure, condensate mass fraction and nucleation rate and total pressure loss has been clarified in case without non-equilibrium condensation upstream of nozzle. The results obtained clearly show that the total pressure loss due to non-equilibrium condensation in the Ludwieg tube should not be neglected even for a very low initial relative humidity and it is resulted from the periodic excursions of the condensation shock wave.

초음속 노즐에서 발생하는 응축충격파 진동의 피동제어

Rapid expansion of a moist air or a stream through a supersonic nozzle often leads to non-equilibrium condensation shock wave, causing a considerable energy loss in flow field. Depending on amount of latent heat released due to non-equilibrium condensation, the flow is highly unstable or a periodical oscillation accompanying the condensation shock wave in the nozzle. The unsteadiness of the condensation shock wave is always associated with several kinds of instabilities as well as noise and vibration of flow devices. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for the purpose of alleviation of the condensation shock oscillations in a transonic nozzle. A droplet growth equation is coupled with two-dimensional Navier-Stokes equation system. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft wind tunnel is made to validate the present computational results. The results show that the oscillations of the condensation shock wave are completely suppressed by the current passive control method.

Bleed Slot을 사용한 응축충격파의 피동제어

The current study describes experimental and computational works on the passive control of the steady and unsteady condensation shock waves, which are generated in a transonic nozzle. The bleed slots are installed on the contoured wall of the transonic nozzle in order to control the magnitude of the condensation shock wave and its oscillations. For computations, a droplet growth equation is copuled with two-dimensional Navier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. An experiment using an indraft transonic wind tunnel is made to validate the computational results. The current computations represented well the experimental flows. From both the experimental and computational results it is found that the magnitude of the condensation shock wave in the bleed slotted nozzle is significantly reduced, compared with no passive control of solid wall. The oscillations of the condensation shock wave are successfully suppressed by a bleed slot system.

천음속 노즐에서 발생하는 응축충격파의 피동제어

A rapid expansion of the moist air or stream through transonic nozzle often leads to not-equilibrium condensation shock, causing a considerable amount of energy loss to the entire flow field. Depending on amount of heat released, condensation shock wave occurs in the nozzle and interacts with the boundary layer flow. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for purpose of alleviation the condensation shock wave in a transonic nozzle. A droplet growth equation is incorporated into two-dimensional wavier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft transonic wind tunnel is made to validate the present computational results. The results obtained show that the magnitude of condensation shock wave is reduced by the current passive control method.

Avoidance of Self-excited Oscillation of Condensation Shock Wave Using a Double Slot.

The current study describes experimental and computational works on the passive control of the unsteady condensation shock wave which is generated in a transonic nozzle. The bleed slots were installed on the contoured wall of the transonic nozzle in order to control the condensation shock wave. For computation, the two dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, were numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin-Lomax turbulence model was employed to close the governing equations. An experiment using an indraft transonic wind tunnel was made to validate the computational results. The current computations represented well the experimental flows. From both experimental and computational results it was found that the oscillations of the condensation shock wave were successfully suppressed by the bleed slot system.

CFD Investigation on Passive Control of Condensation Shock Wave. In Case of Steady Condensation Shock.

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to nonequilibrium condensation phenomena. Thereby, the nozzle flow is affected by the latent heat released by condensation of water vapor. Many papers for the passive control of shock-boundary layer interaction using the porous wall with a plenum underneath have been reported on the application of the technique to transonic airfoil flows. In this paper, this passive technique is applied to a steady condensation shock wave generated in a supersonic nozzle. For the effect of the passive shock-boundary layer control on steady condensation shock, Navier-Stokes equations were solved numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second-order fractional-step for time integration. As a result, the state of flow field has been clarified.

CFD Investigation on Passive Control of Condensation Shock Wave. In Case of Unsteady Condensation Shock.

A rapid expansion of moist air or steam through supersonic nozzle often leads to nonequilibrium condensation shock. Depending on the heat amount released by condensation of water vapour, the flow is highly subject to a periodic oscillation of condensation shock in the nozzle. The unsteadiness of the condensation shock is always associated with several kinds of instabilities as well as noise and vibration of the flow system. In this paper, a passive technique using a porous wall with a plenum cavity underneath is applied for the purpose of alleviation of the condensation shock oscillations in a supersonic nozzle. A droplet growth equation was incorporated into two-dimensional Navier Stokes equation systems. Computations are carried out using a 3rd-order MUSCL type TVD finite difference scheme with a 2nd-order fractional time step. As a result, the oscillations of the condensation shock wave are completely suppressed by the present passive control method.

Passive control of steady condensation shock wave

Passive control of steady condensation shock wave

Passive control of unsteady condensation shock wave

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to nonequilibrium condensation phenomena. Thereby, if the heat released by condensation of water vapour exceeds a certain quantity, the flow will become unstable and periodic flow oscillations of the unsteady condensation shock wave will occur. For the passive control of shock-boundary layer interaction using the porous wall with a plenum underneath, many papers have been presented on the application of the technique to transonic airfoil flows. In this paper, the passive technique is applied to three types of oscillations of the unsteady condensation shock wave generated in a supersonic nozzle in order to suppress the unsteady behavior. As a result, the effects of number of slits and length of cavity on the aspect of flow field have been clarified numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second-order fractional-step for time integration.

114 非定常凝縮衝撃波のパッシブコントロールに関する数値解析

114 非定常凝縮衝撃波のパッシブコントロールに関する数値解析

A Passive Control of Interaction of Condensation Shock Wave anc Boundary Layer(II)

There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable passive effect than the cases of its opposite. opposite.

Passive control of condensation shock wave in supersonic nozzles

When a moist air is rapidly expanded in a supersonic nozzle, nonequilibrium condensation occurs at a supersaturation state. Condensation shock wave appears in the nozzle flow if the releasing latent heat due to condensation goes beyond a critical value. It has been known that self-excited oscillations of the condensation shock wave generate in an air or a steam nozzle flow with a large humidity. In the present study, the passive control technique using porous wall with a cavity underneath was applied to the condensation shock wave. The effects of the passive control on the steady and self-excited condensation shock waves were experimentally investigated by Schlieren visualization and static pressure measurements. The result shows that the present passive control is a useful technique to suppress the self-excited oscillations of condensation shock wave.

A unified theory of aerodynamic and condensation shock waves in vapor-droplet flows with or without a carrier gas

A unified theory for aerodynamic and condensation shock waves in vapor-droplet flows in the presence of an inert carrier gas is presented. Same conservation equations apply across discontinuous models for both types of wave. Exact (as well as approximate), explicit analytical jump conditions across such discontinuities are derived subject to several boundary conditions. Collectively they may be called the generalized Rankine–Hugoniot equations for vapor-droplet mixtures. All the equations derived are general and can be applied in the case of a pure vapor-droplet flow by letting the mass fraction of the carrier gas go to zero. Much physical insight may be obtained from this integral analysis. It is shown that four types of aerodynamic shock waves (viz., equilibrium partly dispersed, equilibrium fully dispersed, partly dispersed with complete evaporation, and fully dispersed with complete evaporation) may occur. Conditions for each type of these waves to occur are specified and the appropriate jump conditions are derived. A flow map for different types of condensation discontinuities to occur is deduced. It is shown that the same jump conditions are applicable for most supersonic and subsonic condensations—both homogeneous and heterogeneous. However, for certain types of condensation shocks predicted by the integral jump conditions, consideration of nonequilibrium gas dynamics must be called for. As a sequel to the integral analysis, time-marching solutions for different types of condensation shock waves in a convergent–divergent nozzle are presented, which include some novel solutions. Isentropic exponents for gas–vapor-droplet flow under frozen and equilibrium conditions are formulated. Gasdynamic equations for vapor-droplet flow, including area variation and interphase transport of mass, momentum, and energy, are derived. It is shown that equations in this full form are to be considered for making correct physical interpretations, e.g., determining the conditions for thermal choking.

101 ダブルスロットによる凝縮衝撃波の制御

Since the concept of passive control of shock-boundary layer interaction using a double slot was published in 1984, several papers have been reported on the application of this technique to transonic airfoil flows. In the present paper, this technique is applied to condensation shock wave which is caused by rapid expansion of moist air in a supersonic nozzle. The effects of passive control on condensation shock wave have been experimentally investigated by a schlieren optical method and pressure measurements. As a result, it is found that the passive control is the useful technique to suppress the periodic oscillation of condensation shock wave.