Direct numerical simulations of supersonic turbulent boundary layer with streamwise-striped wall blowing

On the drag reduction mechanism of hypersonic turbulent boundary layers subject to heated wall blowing

“…Even under hypersonic conditions, the drag reduction control method of TBL based on heated wall blowing can still achieve the superposition effect of wall blowing and wall heating. However, compared with the results in supersonic TBL [26], the drag reduction efficiency of wall blowing/heated wall blowing is greatly reduced under hypersonic conditions, and the drag reduction rate is almost reduced by half, which is due to the strong compressibility of the hypersonic turbulent boundary layer. The strong compressibility of the main flow suppresses the wall-normal fluctuating velocity of the turbulent boundary layer, which weakens the "virtual wall" effect produced by the flow control method.…”

“…Then, we can get the net energy saving rate S, which is defined as Figure 7 draws the corresponding drag reduction benefit graphs under different control methods. The drag reduction results of the supersonic turbulent boundary layer in reference [26], opposing control by Choi [36], uniform blowing by Kametani [15], and steady streamwise near-wall force by Xu [37] are also shown in the figure. First, it is not difficult to see that the net gain under hypersonic conditions is lower than that under supersonic TBL, indicating that the strong compressibility reduces the control efficiency.…”

“…The spanwise width of each slot is also equal to Δz + = 52. Note that different spacing and widths of the streamwise-aligned slots have been investigated in a previous paper [26], only to find that the drag reduction rate is independent of these parameters. Four cases with different combinations of wall-normal blowing amplitude v b and slot temperature T slot are conducted.…”

“…To achieve a better drag reduction effect, breaking through the defects of a single flow control technique and developing a new turbulence drag reduction method combining multiple means will become a research hotspot. Recently, the author proposed a novel velocity-temperature coupled control method using wall heating blowing, which had been applied on supersonic TBLs [26,27]. This method couples the advantages of traditional wall blowing and wall heating control.…”

Current state and future trends in boundary layer control on lifting surfaces

“…The possibilities of reducing drag of a spatially developing supersonic turbulent boundary layer by pulsed wall blowing are numerically investigated (by DNS) by Liu et al 110 Different blowing slot spacings and widths are considered, as well as blowing amplitudes. The authors report that drag reduction spanning 7%–15% was achieved.…”