摘要:

An experimental and numerical study of transient shock wave phenomena in a liquid containing noncondensable gas bubbles is presented. Experiments are done in a shock tube with an upwardly directed bubbly flow to obtain a uniform spatial distribution of bubbles. The bubbly flow has an initial gas volume fraction of 0.2&percent;. The bubbles have a radius of 0.6 mm. The liquid used is a silicone oil whose kinematic viscosity is50×10−6 m2/s.Nitrogen andSF6gas bubbles are tested to bring out the thermal effects of the bubble interior. The numerical calculation is performed using a modified mathematical model based on Kameda and Matsumoto [Phys. Fluids8, 322 (1996)]. The transient pressure profiles determined in the experiment for the upwardly bubbly flow agree well quantitatively with those obtained by the numerical calculation using a uniform spatial distribution of bubbles. TheSF6experiment shows that the radial motion of the bubbles should be estimated by solving an equation in which the liquid compressibility is taken into account. ©1998 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869779

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The problem of stabilization of the hydrodynamic flame instability due to collision of a flame with a weak shock is revised. It is shown that correct treatment of this problem leads to results different from the Markstein solution [G. H. Markstein,Nonsteady Flame Propagation(Pergamon, Oxford, 1964)]. It is obtained that depending on the shock intensity a flame-shock collision may lead to temporary reduction of the perturbation amplitude at the flame front, to complete suppression of initial perturbations, or to inversion of the flame shape. Scalings for the shock intensity leading to stabilization or destabilization of a flame front are obtained. ©1998 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869780

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Hypersonic gas flow over cones is solved using computational fluid dynamics to obtain accurate boundary layer profiles. A linear stability analysis is performed on the profiles to determine the amplification rates of naturally occurring disturbances, and this information is used with theeNmethod to predict the boundary layer transition location. The effects of free-stream total enthalpy and chemical composition on transition location are studied to give a better understanding of recent experimental observations. Namely, there is an increase in transition Reynolds number with increasing free-stream total enthalpy, and this increase is greater for gases with lower dissociation energies. The results show that linear stability predicts the same trends that were observed in the experiments, but withN=10,it consistently overpredicts the transition Reynolds numbers by about a factor of 2. The results of numerical experiments are presented which show the effect of reaction endo- or exothermicity on disturbance amplification rates. ©1998 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869781

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The ability of the velocity ratio parameter&lgr;=(U1−U2)/(U1+U2)to scale linear stability amplification rates for a compressible reacting and compressible variable-density mixing layer is reported. Extensions to the definition of &lgr; to reflect the dominance of outer modes in the flow structure at significant levels of heat release and compressibility are proposed and their performance is evaluated. ©1998 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869786

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The rotational relaxation of nitrogen through high total temperature shock waves is studied using the direct simulation Monte Carlo method coupled with classical trajectory calculations. The results are obtained for the extended Morse potential employed previously for low total temperature shock waves and agree well with the experimental results of Smith and Alsmeyer except Smith’s data in the rearward portion of the shock wave. ©1998 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869782

出版商:AIP    

年代:1998

数据来源: AIP