نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه تبدیل انرژی، دانشکده مهندسی مکانیک، دانشگاه تربیت مدرس، تهران، ایران
2 تربیت مدرس
3 شریف*مکانیک
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Numerical investigation of Transition is one of the challenging issues in turbulence modeling, both in the external and internal flows. In the present study, the coefficients of the four-equation γ-Reθ model are modified based on the physics of internal flow transition to capture the entrance length of the internal flow. The entrance length has a significant influence on industrial applications, including the design of flow-meter systems and wind tunnels. To validate the model, the internal flow is simulated using six different test cases. A 3-D duct, Two smooth axisymmetric pipes, a 3-D stenosis pipe, two parallel plates, and the backward-facing step configurations are considered at different Reynolds numbers from 2103 to 3105. The flow variables, including the average velocity field, friction factor, fully developed friction factor, and the reattachment length are compared against the experimental, theoretical and large eddy simulation results. By comparing the results of average velocity against the semi-empirical relations and experimental data using new coefficients, it is observed the model could estimate the entrance length of the internal flow in accordance with experiments. The earlier coefficients lead to a reduction of entrance length by increasing Reynolds number. Furthermore, the error percentage reduce more than 7.6 and 26.7 percent using new coefficients rather than earlier models to predict the flow variables including fully developed friction factor and reattachment length, respectively.
کلیدواژهها [English]
)