Deflection of a two-dimensional natural convection wake due to the presence of a vertical surface in close proximity

1989 ◽  
Vol 201 (-1) ◽  
pp. 35 ◽  
Author(s):  
Ravindra Agarwal ◽  
Yogesh Jaluria
Keyword(s):  
Natural Convection ◽  
Vertical Surface ◽  
Two Dimensional ◽  
Close Proximity

Grid-Free Vortex Methods for Natural Convection in Two-Dimensional Domains

2012 ◽  
Author(s):  
Issam Lakkis
Keyword(s):  
Natural Convection ◽  
Nonlinear Diffusion ◽  
Reacting Flows ◽  
Ideal Gas ◽  
Two Dimensional ◽  
Vortex Methods ◽  
Free Vortex ◽  
Low Mach Number ◽  
Buoyancy Driven Flows ◽  
Vorticity Generation

Vortex methods for simulating natural convection of an ideal gas in unbounded two-dimensional domains are presented. In particular, the redistribution method for diffusion is extended to enable simulation of nonlinear diffusion of an ideal gas in isobaric conditions encountered in unbounded low-Mach number flows. We also address the problem of handling source terms in grid-free vortex methods and propose a fast, accurate, and physically motivated method for solving the associated inverse problems. Examples include generation of baroclinic vorticity in non-reacting buoyancy driven flows, and in addition, generation of internal energy and species in buoyant reacting flows. Accuracy and speed of the proposed algorithms for nonlinear diffusion and vorticity generation are investigated separately. Simulations of natural convection of a “thermal patch” for Grashof number ranging from to 1562.5 to 25000 are presented.

The Aerodynamics of Three-Dimensional Vaned Diffusers in Industrial Centrifugal Compressors

2005 ◽  
Author(s):  
Ahmed Abdelwahab
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Pressure Recovery ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Two Dimensional ◽  
Blade Loading ◽  
Recovery Capacity ◽  
Close Proximity

Vaned diffusers have been used successfully as efficient and compact dynamic pressure recovery devices in industrial centrifugal compressor stages. Typically such diffusers consist of a cascade of two-dimensional blades distributed circumferentially at close proximity to the impeller exit. In this paper three low-solidity diffuser blade geometries are numerically investigated. The first geometry employs variable stagger stacking of similar blade sections along the blade span. The second employs linearly inclined stacking to generate blade lean along the diffuser span. The third geometry employs the conventional two-dimensional low-solidity diffuser geometry with no variable stagger or lean. The variable stagger blade arrangement has the potential of better aligning the diffuser leading edges with the highly non-uniform flow leaving the impeller. Both variable stagger and linearly leaned diffuser blade arrangements, however, have the effect of redistributing the blade loading and flow streamlines in the spanwise direction leading to improved efficiency and pressure recovery capacity of the diffuser. In this paper a description of the proposed diffuser geometries is presented. The results of Three-dimensional Navier-Stokes numerical simulations of the three centrifugal compressor arrangements are discussed. Comparisons between the performance of the two and three-dimensional diffuser blade geometries are presented. The comparisons indeed show that the variable stagger and leaned diffusers present an improvement in the diffuser operating range and pressure recovery capacity over the conventional two-dimensional diffuser geometry.

Measurements and Calculations of Transient Natural Convection in Water

1982 ◽  
Vol 104 (4) ◽  
pp. 644-648 ◽  
Author(s):  
B. Sammakia ◽  
B. Gebhart ◽  
Z. H. Qureshi
Keyword(s):  
Natural Convection ◽  
Temperature Response ◽  
Vertical Surface ◽  
Constant Heat Flux ◽  
Thermal Capacity ◽  
Transient Natural Convection ◽  
Heating And Cooling ◽  
Dependent Form ◽  
Induced Flow ◽  
Explicit Finite Difference

Transient natural convection adjacent to a flat vertical surface with appreciable thermal capacity is investigated both experimentally and numerically. The surface is immersed in initially quiescent water, and has the same uniform temperature distribution. It is then suddenly loaded with a uniform and constant heat flux thereby generating a buoyancy induced flow adjacent to the surface. Surface temperature response was recorded by means of thermocouples embedded inside the surface, and boundary layer temperature measurements were also taken. An explicit finite difference numerical scheme is used to obtain solutions to the partial differential equations describing the conservation of mass, momentum, and energy in their time dependent form. Good agreement between the calculated and measured results is observed for both the heating and cooling transient processes.

Natural Convection Heat Transfer From an Isothermal Vertical Surface to a Stable Thermally Stratified Fluid

1992 ◽  
Vol 114 (4) ◽  
pp. 917-923 ◽  
Author(s):  
D. Angirasa ◽  
J. Srinivasan
Keyword(s):  
Natural Convection ◽  
Thermal Stratification ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Stratified Fluid ◽  
Vertical Surface ◽  
Natural Convection Heat Transfer ◽  
Plate Temperature ◽  
Transient Nature ◽  
Wide Range

Natural convection from an isothermal vertical surface to a thermally stratified fluid is studied numerically. A wide range of stratification levels is considered. It is shown that at high levels of ambient thermal stratification, a portion at the top of the plate absorbs heat, while a horizontal plume forms around a location where the plate temperature equals the ambient temperature. The plume is shown to be inherently unsteady, and its transient nature is investigated in detail. The effect of the temperature defect in striating the plume is discussed. Average Nusselt number data are presented for Pr=6.0 and 0.7.

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