Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental dat...Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental data.Flow structures are described and impingement heat transfer characteristics are discussed.The effects of Re,H/B and D/B on single-slot jets impingement heat transfer are analyzed and heat transfer characteristics of multiple-slot jets are investigated.The results show that:Gas flows along the convex surface and boundary layer separation occurs in both single and multiple-slot jets impingement.A maximum stagnation Nu appears at H/B=8 and the local Nu decreases with increasing H/B in the region far away from the stagnation.The Nu in the stagnation region decreases with increasing D/B but the Nu is nearly the same in the region far away from the stagnation.Pressure gradient is an important factor on heat transfer enhancement.Correlations of the Num for single-slot,double-slot and quadric-slot jets impinging on a convex surface are obtained.It indicates the effects of Re and D/B on Num could become more important in less slot jets impingement.展开更多
In this paper, Numerical simulations of mean velocity and turbulent kinetic energy fields are presented for three-dimensional lateral jet in crossflow, at the injection angles of -60° and -30 °. The RNG κ- ...In this paper, Numerical simulations of mean velocity and turbulent kinetic energy fields are presented for three-dimensional lateral jet in crossflow, at the injection angles of -60° and -30 °. The RNG κ- ε turbulence model, with the two-layer wall function method, is adopted to simulate the characteristics of this flow at the jet-to-crossflow velocity ratios, 1, 2 and 4. The results show that the injection angle and jet-to-crossflow velocity ratio can change the flow fields, and the range upstream affected by jet injected laterally increase and the curvature of jet trajectories varies along the flow direction. Furthermore, the separation events in the lee of the jet exit and behind the jet bending-segment have been found, and the mechanisms of two vortex systems are analyzed.展开更多
The standard k ε turbulence model in conjunction with the logarithmic law of the wall has been applied to the prediction of a fully developed turbulent slot impinging jet within a semi confined space. A single geo...The standard k ε turbulence model in conjunction with the logarithmic law of the wall has been applied to the prediction of a fully developed turbulent slot impinging jet within a semi confined space. A single geometry with a Reynolds number of 10,000 and a nozzle to plate spacing of eight slot widths has been considered with inlet boundary conditions based on the previous calculated result of a fully developed turbulent 2 D flow. The numerical results of mean velocity agree with the experimental data. But the fluctuating velocity is somewhat poorly predicted. The difference between the numerical study and the experimental data is attributed directly to the turbulence model, and the application of the wall function.展开更多
文摘Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental data.Flow structures are described and impingement heat transfer characteristics are discussed.The effects of Re,H/B and D/B on single-slot jets impingement heat transfer are analyzed and heat transfer characteristics of multiple-slot jets are investigated.The results show that:Gas flows along the convex surface and boundary layer separation occurs in both single and multiple-slot jets impingement.A maximum stagnation Nu appears at H/B=8 and the local Nu decreases with increasing H/B in the region far away from the stagnation.The Nu in the stagnation region decreases with increasing D/B but the Nu is nearly the same in the region far away from the stagnation.Pressure gradient is an important factor on heat transfer enhancement.Correlations of the Num for single-slot,double-slot and quadric-slot jets impinging on a convex surface are obtained.It indicates the effects of Re and D/B on Num could become more important in less slot jets impingement.
文摘In this paper, Numerical simulations of mean velocity and turbulent kinetic energy fields are presented for three-dimensional lateral jet in crossflow, at the injection angles of -60° and -30 °. The RNG κ- ε turbulence model, with the two-layer wall function method, is adopted to simulate the characteristics of this flow at the jet-to-crossflow velocity ratios, 1, 2 and 4. The results show that the injection angle and jet-to-crossflow velocity ratio can change the flow fields, and the range upstream affected by jet injected laterally increase and the curvature of jet trajectories varies along the flow direction. Furthermore, the separation events in the lee of the jet exit and behind the jet bending-segment have been found, and the mechanisms of two vortex systems are analyzed.
文摘The standard k ε turbulence model in conjunction with the logarithmic law of the wall has been applied to the prediction of a fully developed turbulent slot impinging jet within a semi confined space. A single geometry with a Reynolds number of 10,000 and a nozzle to plate spacing of eight slot widths has been considered with inlet boundary conditions based on the previous calculated result of a fully developed turbulent 2 D flow. The numerical results of mean velocity agree with the experimental data. But the fluctuating velocity is somewhat poorly predicted. The difference between the numerical study and the experimental data is attributed directly to the turbulence model, and the application of the wall function.
