Takahiro Tamba

Laser energy deposition effectiveness on shock-wave boundary-layer interactions over cylinder-flare combinations

The effects of repetitive laser-pulse energy depositions (5.5 mJ/pulse) onto a shock wave-boundary layer interaction region over cylinder-flare model in a Mach 1.92 flow are experimentally investigated. Depending on the nose shape and the flare angle, the flow patterns are subdivided to two; separated flow in which a slip line and a strong separation shock wave originated in the nose-cylinder junction appears, and a non-separated flow in which a slip line is not observed and the re-attachment shock wave is much weaker. At flare angles around 30°, the separation can be suppressed by laser energy deposition even of down to 5 kHz. The Schlieren-visualized flow patterns are well correlated to the drag characteristics, in which a larger drag is obtained without separation. A possible scenario of the separation control is that the disturbance introduced by the baroclinic vortex ring induced the boundary layer transition so that it became robust against the adverse pressure gradient. Under marginal conditions, dual mode flow patterns, that is, a partial and full suppression modes are obtained under the same operation conditions.

Frequency modulation in shock wave-boundary layer interaction by repetitive-pulse laser energy deposition

Modulation of shock foot oscillation due to energy deposition by repetitive laser pulses in shock wave-boundary layer interaction over an axisymmetric nose-cylinder-flare model in Mach 1.92 flow was experimentally studied. From a series of 256 schlieren images, density oscillation spectra at each pixel were obtained. When laser pulses of approximately 7 mJ were deposited with a repetition frequency, fe, of 30 kHz or lower, the flare shock oscillation had a peak spectrum equivalent to the value of fe. However, with fe of 40 kHz–60 kHz, it experienced frequency modulation down to lower than 20 kHz.

Laser Energy Deposition for Shock Wave Boundary Layer Control at Supersonic Speeds

Shock Wave Boundary Layer Interactions (SWBLIs) can induce separation which causes loss of a control surface effectiveness, drop of an air intake efficiency and it may be the origin of large scale fluctuations such as air-intake buzz, buffeting or fluctuating side loads in separated propulsive nozzles

Experimental Investigation of Normal Shock Wave-Counter Flow Interactions

The interactions between a shock wave and various flows are important research subjects in various fields. Investigations of shock wave interaction with hot bubbles and that with turbulence lead to important applications in aerospace engineering. Energy deposition in supersonic flow has been investigated in recent years as the method to moderate a shock wave and reduce the wave drag. Previous results showed the drag was reduced by up to 21 % with laser-induced bubbles at Mach number of 1.92 flow [1]. Yet, if hot bubbles are connected with each other to form a long column, the drag reduction is expected to be much enhanced [2]. The shock wave-hot bubble column interaction was investigated using a single shock tube and a repetitive pulse laser; however the deformation of the shock wave was not observed because of the limitation of the facility performance [3]. Also, the interaction between a weak shock wave and turbulence has been investigated in order to understand basic processes of sonic boom propagating through the atmospheric turbulence. Some reports indicated that a weak shock wave is greatly modulated by the turbulence [4]; however the mechanisms of the modulation have not been well understood.

Control of Unsteadiness in Shock Wave–Boundary Layer Interaction by Repetitive Laser Energy Deposition

Shock wave–boundary layer interaction (SWBLI) causes serious problems against realizing supersonic transport, such as flow unsteadiness which leads to degradation of engine performance, wing lift capacity and control surfaces effectiveness, and heat transfer and pressure loads which reduce the endurance of aircraft structures.

Effects of Repetitive Laser Energy Deposition on Supersonic Duct Flows

An experimental study was conducted to examine the effects of repetitive energy deposition on the supersonic flow characteristics over a duct system with a central conical compression surface. Boun...

Shock Wave Boundary Layer Interaction Control using Repetitive-Pulse Laser Energy Depositions

Repetitive pulse laser energy deposition can modulate the shock wave oscillation frequency, which caused by shock wave and boundary layer interactions. Without energy deposition, the shock oscillation frequency is lower than 10 kHz. This frequency can be modulated to the repetition frequency of energy deposition. However, the oscillation frequency does not correspond to the energy deposition frequency when the frequency of the repetitive energy deposition become high enough to interact successive vortex rings. At 40 kHz energy deposition, the shock oscillation frequency is lower than 10 kHz, and the strong peak is observed at 1 kHz.