PD Dr. Yan Jin
Eissendorfer Str. 38, bulding O, Room 3.019
Telephone +49 40 42878-4644
E-Mail: PD Dr. Jan Yin.
Turbulence modelling, simulation, and control
A turbulence model with high accuracy and low computational cost, see Jin (2019), has been developed through the DFG-Heisenberg program (299562371). The developed turbulence model has higher accuracy than classic LES and RANS models when the same mesh resolution is used. It is particularly suitable for simulating complex turbulent flows in industry, e.g., flows in turbomachinery (Jin 2020), see Fig. 1. We are also interested in the techniques of controlling turbulence and reducing the corresponding irreversible losses, see Jin & Herwig (2014) and Li, et al. (2021) as examples.
Convection in porous media
Porous media are an important material in nature and industry. Convection in porous media receives a lot of attentions in recent years with the emergence of some new engineering applications, e.g., long term storage of CO2 in deep saline aquifers, thermal energy storage systems using stones/bricks as storage materials, etc. Based on deep investigation of physics, we try to develop efficient and accurate macroscopic models for predicting losses and heat/mass transfer rate in porous media (Fig. 2), see details in Jin, et al. (2015; 2017), Uth, et al. (2016), Kranzien & Jin (2018), Rao, et al. (2020) and Gasow, et al. (2020) for the details of this research. This research is funded by the DFG (408356608).
Flows in biological and physiological processes
Bio-fluid mechanics is an interdisciplinary study which is located at the interface of fluid mechanics and biology. This is a new and promising research field. We are studying the digestion process in human-stomach using a CFD method, see Li & Jin (2021). We have also investigated the “Magenstrasse” based on the numerical results (Fig. 3), see Li, et al. (2021). This research is funded by the Chinese Scholar Council (CSC). In another research topic, we are investigating the flow and particle transportation in a human’s respiratory system (Fig. 4).
|Title: Physical Mechanisms Investigation of Sharkskin-Inspired Compressor Cascade Based on Large Eddy Simulations.|
|Written by: Li, Z.H.; Jin, Y.; Du, J.; Nie, C.; H.W. Zhang|
|in: <em>J. Turbomach.</em>. (2021).|
|Volume: <strong>143</strong>. Number: (6),|
Abstract: To survive in a complex environment, nature has produced efficient and versatile resource-rich structures. One of the novel drag reduction designs comes from the efficient movement of sharks through microscope riblets aligned along the flow direction. In this paper, the effectiveness of sharkskin-inspired riblets in reducing the aerodynamic loss of compressor cascade flow was investigated using the high-fidelity numerical simulation method. Two key normalized parameters, i.e., s+ and h+, were selected to parameterize various riblet designs, and the corresponding relative change in cascade performance was first investigated based on the unsteady Reynolds-averaged Navier–Stokes (uRANS) simulations with/without a transition model. Then, the large eddy simulations in conjunction with the wall-adapted local eddy viscosity model were conducted to investigate the cascade flow with the selected riblet design cases. By comparing the flow resistance, transition positions, vortex formations, and turbulence fluctuations of the boundary flow, the flow control mechanisms of the riblets were finally studied. Simulation results show that compared with the prototype case, the total pressure loss can be reduced by up to 20.5% in the fully turbulent environment. This is because the spanwise fluctuation of the turbulent vortices is impeded inside the boundary layer, and the turbulent vortices are lifted above the riblet tip. Low-speed streaks inside the riblet valleys generate relatively low shear stresses, while the high-shear stresses occur only at the riblet tips. However, when considering the transition from laminar to turbulent boundary flow, the aerodynamic performance of compressor cascade strongly depends on the riblet position relative to the transition region on cascade suction side (SS). The total pressure loss can only be reduced by up to 8.1%, and even most riblet designs degrade the cascade performance. The major reason is that the riblets are located upstream of the transition zone, especially at the small incidence angles. Due to the installation of riblets, the contact area between the laminar flow and the wall surface is increased, and the downstream laminar-to-turbulent transition is promoted.