摘要:

We report experimental results concerning patterns in a model experiment built to study buoyant-thermocapillary-driven flows. The fluid is situated in a cooled cylindrical container and locally heated on its free surface. The resulting temperature gradient induces a basic flow which draws the surface fluid from the hot center toward the cold boundary. When the gradient is increased and depending on the height of liquid, the basic flow destabilizes into different stationary patterns. Above a second threshold, the patterns become time-dependent. These different instabilities are characterized and compared to recent theoretical results. ©1997 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869470

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An asymptotic order-of-magnitude description is given of the structure of a circular laminar hydraulic jump for large values of the Reynolds and Froude numbers of the flow entering the jump. The results are compared with numerical solutions of the boundary layer equations for the flow in a liquid layer on a horizontal disk and with experimental results existing in the literature. ©1997 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869272

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The flow field with vortex breakdown in wide spherical gaps was studied numerically by a finite difference method under the axisymmetric condition. The result shows that the flow bifurcates to periodic motion as the Reynolds number or the eccentricity of the spheres increases. ©1997 American Institute of Physics. 

ISSN:1070-6631    

DOI:10.1063/1.869269

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effect of extreme hyperviscous damping,&ngr;knp,p=∞is studied numerically in the GOY shell model of turbulence. It has resently been demonstrated [Leveque and She, Phys. Rev. Lett.75, 2690 (1995)] that the inertial range scaling in the GOY model is non-universal and dependent on the viscous damping. In the present study it is shown that the deviation from Kolmogorov scaling is due to the cascade of the second inviscid invariant. This invariant is non-positive definite and in this sense analogous to the helicity of 3D turbulent flow. ©1997 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869270

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Scale similarity models are discussed for the subgrid-scale stress tensor and subgrid-scale variance of a passive scalar in a turbulent flow. The modeling involves sampling of the resolved fields by applying a spatial filter at a scale greater than the grid spacing of the computational mesh. A method is described for determining the constant of proportionality present in each model. The model constant for the subgrid-scale stress tensor is determined such that the subgrid-scale turbulent kinetic energy is exact on average. The constant is shown to depend on the size of the sampling filter, the turbulence Reynolds number and the degree of resolution of the large eddies. ©1997 American Institute of Physics.

ISSN:1070-6631    

DOI:10.1063/1.869271

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:1070-6631    

DOI:10.1063/1.869522

出版商:AIP    

年代:1997

数据来源: AIP