The Heat Transfer and Coherent Structures of the Tangential Impingement Jets in the Annular Chamber Studied With Extended Proper Orthogonal Decomposition

Abstract The tangential impingement of turbulent circular jets on the cylindrical surface in an annular chamber is numerically investigated based on the SAS-SST model. The main purpose is to understand the role of the coherent structures on the temperature field inside the chamber and the heat transfer coefficient field on the hub surface. Based on the jet diameter and inlet velocity, the jet Reynolds numbers are given as 285000, 332000, and 392000, respectively. The accuracy of the numerical simulation is verified by the experimental data. The spectrum information of the velocity magnitude at the monitor point is obtained by the fast Fourier transform (FFT) method. An improvement of the proper orthogonal decomposition (POD) method is known as the extended POD (EPOD) method, which is mainly suitable for analyzing the correlation between the flow field and the synchronized scalar or vector fields, such as the correlation between the velocity and the heat transfer coefficient fields. In present study, both the POD method and the EPOD method are applied and compared. The POD method allows to visualize the main modes in terms of velocity, temperature, and heat transfer coefficient fluctuations. With the help of the EPOD method, the contribution of velocity fluctuations to temperature fluctuations in the chamber and heat transfer fluctuations on the hub surface are further analyzed. For Rej = 392000, the first two velocity POD modes and the velocity EPOD modes that contribute the most to the temperature fluctuations are very similar, reflecting the same large-scale coherent structures. The first two velocity EPOD modes that contribute the most to the heat transfer coefficient fluctuations have a high proportion of energy in the flow field, corresponding to the deflection motion of the jet.