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ABSTRACT
Turbulent fluid flows with a swirl occur in numerous engineering practice situations. Five widely recognized turbulence models were evaluated using experimental results. Among the RANS-based two-equation models, the SST κ–ω model proved to be the most effective. The predictions obtained from a LES turbulence model were slightly better, however there was an enormous difference in the CPU time. The CPU time needed for the LES solution was 155.3 days, whereas it was only 14.2 days for the SST κ–ω solution. In this light, it is believed that the SST κ–ω model is the most efficient of those investigated. An important input for the numerical simulation of turbulent flow and heat transfer is the turbulence intensity at the inlet of a solution domain. For the evaluation of turbulence models, use was made of the measured turbulence quantities from the verification experiments. More often, simulations are executed based on the uniform values of the turbulence intensity across the inlet. The errors in the heat transfer results due to this practice are evaluated and are shown to be significant.
Nomenclature
| D | = | inlet diameter |
| Cp | = | specific heat |
| Cw | = | LES model constant |
| Cε1, Cε2, Cε2RNG | = | turbulence model constants |
| Cμ, CμRNG | = | turbulence model constants |
| F1, F2 | = | blending functions in the SST model |
| h | = | heat transfer coefficient |
| k | = | thermal conductivity |
| kturb | = | turbulent thermal conductivity |
| NuD | = | Nusselt number based on inlet diameter |
| p | = | pressure |
| Pk | = | production term for the turbulent kinetic energy |
| Prtur | = | turbulent Prandtl number |
| q | = | wall heat flux |
| r | = | radial coordinate |
| S | = | shear strain rate |
| t | = | time |
| T | = | temperature |
| u | = | velocity component |
| Uo | = | mean axial velocity |
| u′, v′, w′ | = | fluctuating velocity component |
| x | = | coordinate |
| y | = | coordinate |
| y+ | = | nondimensional near-wall mesh quality metric |
| z | = | axial coordinate |
| Greek symbols | = | |
| α1, α3 | = | turbulence model constants |
| β1, β, βRNG | = | turbulence model constants |
| Δ | = | element volume |
| ε | = | turbulence dissipation |
| κ | = | turbulent kinetic energy |
| μ | = | molecular viscosity |
| μsgs | = | small-scale eddy viscosity |
| µt | = | turbulent eddy viscosity |
| ρ | = | fluid density |
| σ | = | Prandtl-number-like diffusion coefficient |
| σε, σεRNG | = | turbulence model constants |
| σκ, σκ3, σκRNG | = | turbulence model constants |
| σω, σω2 | = | turbulence model constants |
| τ | = | shear stress |
| ω | = | specific rate of turbulence dissipation |
| Ω | = | vorticity tensor |
| Subscripts | = | |
| b | = | bulk (mass-weighed average) |
| i | = | index notation for Cartesian coordinates |
| j | = | index notation for Cartesian coordinates |
| k | = | index notation for Cartesian coordinates |
| m | = | index notation |
| n | = | index notation |
| w | = | wall |
Nomenclature
| D | = | inlet diameter |
| Cp | = | specific heat |
| Cw | = | LES model constant |
| Cε1, Cε2, Cε2RNG | = | turbulence model constants |
| Cμ, CμRNG | = | turbulence model constants |
| F1, F2 | = | blending functions in the SST model |
| h | = | heat transfer coefficient |
| k | = | thermal conductivity |
| kturb | = | turbulent thermal conductivity |
| NuD | = | Nusselt number based on inlet diameter |
| p | = | pressure |
| Pk | = | production term for the turbulent kinetic energy |
| Prtur | = | turbulent Prandtl number |
| q | = | wall heat flux |
| r | = | radial coordinate |
| S | = | shear strain rate |
| t | = | time |
| T | = | temperature |
| u | = | velocity component |
| Uo | = | mean axial velocity |
| u′, v′, w′ | = | fluctuating velocity component |
| x | = | coordinate |
| y | = | coordinate |
| y+ | = | nondimensional near-wall mesh quality metric |
| z | = | axial coordinate |
| Greek symbols | = | |
| α1, α3 | = | turbulence model constants |
| β1, β, βRNG | = | turbulence model constants |
| Δ | = | element volume |
| ε | = | turbulence dissipation |
| κ | = | turbulent kinetic energy |
| μ | = | molecular viscosity |
| μsgs | = | small-scale eddy viscosity |
| µt | = | turbulent eddy viscosity |
| ρ | = | fluid density |
| σ | = | Prandtl-number-like diffusion coefficient |
| σε, σεRNG | = | turbulence model constants |
| σκ, σκ3, σκRNG | = | turbulence model constants |
| σω, σω2 | = | turbulence model constants |
| τ | = | shear stress |
| ω | = | specific rate of turbulence dissipation |
| Ω | = | vorticity tensor |
| Subscripts | = | |
| b | = | bulk (mass-weighed average) |
| i | = | index notation for Cartesian coordinates |
| j | = | index notation for Cartesian coordinates |
| k | = | index notation for Cartesian coordinates |
| m | = | index notation |
| n | = | index notation |
| w | = | wall |