Numerical simulations of attachment-line boundary layer in hypersonic flow, Part II: the features of three-dimensional turbulent boundary layer

TL;DR

This paper investigates three-dimensional turbulent boundary layers in hypersonic flow, revealing how transverse flow and pressure gradients influence velocity profiles, shear stresses, and energy distribution, with implications for modeling such flows.

Contribution

It provides new insights into the effects of transverse flow and pressure gradients on 3D turbulent boundary layers, extending classical two-dimensional theories to three-dimensional hypersonic flows.

Findings

Spanwise homogeneity persists without infinite sweep assumption.

Classical velocity transformation holds with transverse velocity and pressure gradient.

Pressure gradient reduces accuracy of temperature-velocity relationships.

Abstract

In this study,we investigate the characteristics of three-dimensional turbulent boundary layers influenced by transverse flow and pressure gradients. Our findings reveal that even without assuming an infinite sweep, a fully developed turbulent boundary layer over the present swept blunt body maintains spanwise homogeneity, consistent with infinite sweep assumptions.We critically examine the law-of-the and temperature-velocity relationships, typically applied two-dimensional turbulent boundary layers, in three-dimensional contexts. Results show that with transverse velocity and pressure gradient, streamwise velocity adheres to classical velocity transformation relationships and the predictive accuracy of classical temperaturevelocity relationships diminishes because of pressure gradient. We show that near-wall streak structures persist and correspond with energetic structures in the outer region, though three-dimensional effects redistribute energy to align more with the external flow direction. Analysis of shear Reynolds stress and mean flow shear directions reveals in near-wall regions with low transverse flow velocity, but significant deviations at higher transverse velocities. Introduction of transverse pressure gradients together with the transverse velocities alter the velocity profile and mean flow shear directions, with shear Reynolds stress experiencing similar changes but with a lag increasing with transverse. Consistent directional alignment in outer regions suggests a partitioned relationship between shear Reynolds stress and mean flow shear: nonlinear in the inner region and approximately linear in the outer region.