Akihiro Sasoh

• Nagoya University

When a shock wave encounters an interface with a medium of different acoustic impedance, a reflected wave is generated. It is a shock wave if the medium has a higher acoustic impedance or an expansion fan if the impedance is lower. When the acoustic impedances are perfectly matched, no wave is reflected—a phenomenon known as “impedance matching.” T...

This comprehensive research explores the potential of laser propulsion as a cost-effective alternative for space launches and as a solution for space debris removal. The first part delves into pulsed laser orbital launchers, introducing their principles, examining different vehicle types, and assessing past studies for feasibility in mass space tra...

The shock surface geometry is investigated with direct numerical simulations of a weak normal shock wave propagating in turbulence. The geometry is quantified with the principal curvatures of the surface. A large part of the surface has an approximately flat saddle shape, while elliptic concave and convex shapes with a large curvature intermittentl...

In this study, a layer of cellophane, subjected to an air-pressure difference, was ruptured using a piercing needle. Accordingly, petal-like fragmentation was observed in the layer via high-speed imaging. Two types of crack-propagation regimes were subsequently observed experimentally. If a tensile stress lower than 20.6 MPa acted on the cellophane...

In this study, the effects of thermal bubbles produced by repetitive laser pulses on a shock wave system over a cone with an apex angle of 40° surrounded by a 19 mm×19 mm square duct in a Mach 1.97 flow were experimentally investigated. The shock wave system was controlled by changing the location of the conical centerbody. Depending on the blockag...

View Video Presentation: https://doi.org/10.2514/6.2022-4127.vid In this research, peculiar behaviors in calculations of weak and very-weak moving shock waves by two-dimensional finite volume methods are investigated. First-order accuracy calculations of moving shock wave with a shock Mach number of 1.01 show anomalous solutions. The observed anoma...

View Video Presentation: https://doi.org/10.2514/6.2021-2608.vid Shock wave modulations in interaction with turbulence are important to interpret unsteady shock wave behaviors. Although a recent study by a direct numerical simulation reported that the “vanished” regime of shock-turbulence interaction, such a shock wave profile modulation is not ful...

In this study, losing the shock wave profiles under interactions with grid turbulence was investigated experimentally and theoretically. We demonstrated that the shock wave contrast on side-view schlieren images gradually decreased to an undetectable level in the experiment. This shock wave ‘vanishment’ occurred at a low shock Mach number with a hi...

In this study, unsteady aerodynamic forces induced by forced pitch and heave motions are measured and formulated to the unsteady aerodynamic coefficients by utilizing the 1/4-scale nearly actual vehicle model with wheels and wheel-houses and a system without unnecessary stings exposed to the flow. The unsteady aerodynamic lift forces are measured a...

A high-pressure field is generated in a circular tube by introducing an unsteady jet from its open end. The head of this jet acts as a piston, driving compression waves ahead of it. The peak value of the induced overpressure is evaluated as a solution of a Riemann problem, wherein the jet head is equivalent to a piston head. The jet head of the dri...

When we drive a car on a highway, we occasionally have to press the brake pedal at a sudden traffic jam, the cause of which we do not readily understand.

By utilizing the characteristics of compressible flow, we can generate high-speed flow, high-pressure, and/or high-temperature states. The design of rocket engine nozzle and that of air intake for an aircraft engine need to be conducted based on the principle of compressible fluid dynamics. In this chapter, we will illustrate representative example...

Using the characteristics and invariants dealt with in Chap. 8, an initial value problem with two one-dimensional elements can be solved. This is termed as the Riemann problem, which gives a solution to Euler’s equation that may include a discontinuity. In this chapter, we study Riemann’s solutions in detail and apply them to practical problems.

Pressure waves appearing in this book are categorized in Table 8.1.

Gas and liquid are termed fluid because they can flow with changes to their shape. Most flows occurring in our daily life are not significantly influenced by compressibility. However, in high-speed flows and/or when velocity or pressure rapidly varies, compressibility is significant. The compression and expansion of a fluid, which correspond to var...

When analyzing flow, it is often sufficient to observe the spatiotemporal variation of macroscopic quantities of a continuum fluid, such as the flow velocity and thermodynamic properties, rather than to trace all particles. In this chapter, we will derive the basic equations of compressible fluid dynamics. Although diffusion, viscosity, and heat co...

The static characteristics of a gas are described by thermodynamics. Thermodynamics starts with the formulation of experimentally observed phenomena, following which the formulae are related as results of the behavior of a group of gas particles. Compressible fluid dynamics is also based on thermodynamics. The local motion of gas particles is decom...

Why do we make a small mouth when blowing out candle flames or playing with a mouth whistle? The same question can be applied to a shower, spray, or rocket nozzle, in which high-speed flow is generated by varying the cross-sectional area of a flow passage.

Real flows are usually three dimensional. However, many important flow characteristics appear even in two-dimensional flows. In this chapter, we deal with steady state, two dimensional, supersonic flows. In such flows, compression/shock and expansion waves appear.

A system accompanying a shock wave that exchanges energy and/or momentum with the external environment can enhance the strength of the shock wave or generate a thrust.

In a steady, two-dimensional flow (Chap. 10.1007/978-981-15-0504-1_7) and an unsteady, one-dimensional flow (Chap. 10.1007/978-981-15-0504-1_8), the flow velocity and thermodynamic properties are expressed as functions of two independent variables by applying Euler’s equation. In those cases, the differential equation is hyperbolic and can be solve...

This book offers comprehensive coverage of compressible flow phenomena and their applications, and is intended for undergraduate/graduate students, practicing professionals, and researchers interested in the topic. Thanks to the clear explanations provided of a wide range of basic principles, the equations and formulas presented here can be underst...

Research interest has been growing in recent years in supersonic transport, particularly supersonic propulsion systems. A key component of a commonly studied propulsion system, ramjets, is the air intake. For supersonic propulsion systems a major factor in the overall efficiency is the intake pressure recovery. This refers to the ratio of the avera...

The effects of hollow cathode position on thrust performances of a diverging-magnetic-field electrostatic thruster, which had a diverging magnetic field between a ring anode and a hollow cathode, were investigated. The hollow cathode was located in either a central or an external configuration. Based on the discharge current and direct thrust measu...

This study experimentally investigated the effects of repetitive laser energy deposition using a supersonic intake model with a central conical compression surface and a 19×19 mm2 cross-sectional duct in a Mach 1.92 indraft wind tunnel: especially in the subcritical and buzz modes. A single-pulse energy deposition was observed to suppress the flow...

An impulse generated by laser ablation bas been implicitly assumed to be directed in the normal direction to the irradiation surface. In this study, however, the impulse induced by an Nd:YAG laser pulse with a wavelength of 1.064 μm irradiated on to a macroscopically flat aluminium plate ablator was enhanced in the direction of the laser beam incid...

The impacts of the interaction with grid turbulence of a turbulent Mach number in the range 0.6×10−2 to 2.4×10−2 (representative value) on a planar shock wave with a shock Mach number of about 1.04 were experimentally investigated. Using the counter-driver shock tube with a 120 mm × 120 mm square cross section, the turbulent Mach number level and t...

The shock wave induced by the supersonic flight model and the turbulent flow induced by the free-falling grid were interacted using the time-synchronized launch operating system of the aero-ballistic range. The time-synchronized launch system was successfully done. However, the clear effect of the turbulence on the pressure signature has not been o...

A counter-driver shock tube, which realized a normal shock wave-grid turbulence interaction in various conditions, was developed. Also, a new method to calibrate constant temperature hot-wire anemometer using shock wave experiments was developed. Using the shock tube, an interaction experiment between a normal shock wave (Ms = 1.01) and isentropic...

The shock wave generation in a closed tube using the high-speed jet injection was experimentally investigated. The unsteady behavior of the gas compression by the jet injection was visualized by the schlieren method, and the temporal history of the overpressure was measured by the pressure transducers which flush mounted in a tube. The injected jet...

Impacts of energy deposition approach on performance of supersonic flow over a duct system were experimentally examined. Without using energy deposition, in the case of duct’s normal operation, supersonic flow was found being separated and weakly fluctuating at the duct’s compression surface. Additionally, in the case of unstable operation, superso...

We investigate interactions between a planar shock wave and homogeneous isotropic turbulence by employing direct numerical simulations. The shock wave at the shock Mach numbers 1.5 and 1.1 propagates through the turbulence without mean velocity. The interactions are studied for the statistical properties of turbulence and pressure increase of the s...

Velocity fluctuations of grid turbulence and overpressure of spherical shock wave are measured simultaneously in wind tunnel experiments. The experiments are conducted for four different conditions of grid turbulence, where the turbulent intensity and the length scales are different. Probability density functions (PDFs) of the velocity fluctuation...

Wind tunnel experiments are conducted to clarify the turbulence structure in grid-generated turbulence interacting with a spherical shock wave. The Mach number of the shock wave is 1.04 at the measurement location. Streamwise and vertical velocities are measured by the PIV at two instants. One is immediately after the passage of the shock wave and...

This is the first volume of a two volume set which presents the results of the 31st International Symposium on Shock Waves (ISSW31), held in Nagoya, Japan in 2017. It was organized with support from the International Shock Wave Institute (ISWI), Shock Wave Research Society of Japan, School of Engineering of Nagoya University, and other societies, o...

This is the second volume of a two volume set which presents the results of the 31st International Symposium on Shock Waves (ISSW31), held in Nagoya, Japan in 2017. It was organized with support from the International Shock Wave Institute (ISWI), Shock Wave Research Society of Japan, School of Engineering of Nagoya University, and other societies,...

The thrust characteristics of electrostatic-magnetic hybrid acceleration have been obtained in the central–cathode electrostatic thruster (CC-EST), which has a diverging magnetic nozzle and injects propellant through an annular slit on the inner surface of a ring anode. The electrostatic and electromagnetic contributions are evaluated by fitting ex...

We study the pressure increase across a planar shock wave with shock Mach numbers Ms of 1.1, 1.3, and 1.5 propagating through homogeneous isotropic turbulence at a low turbulent Mach number (Mt ∼ 10⁻⁴) based on direct numerical simulations (DNSs). Fluctuation in the pressure increase, Δp′, on a given shock ray is induced by turbulence around the ra...

The thrust performance of a steady-state, applied-field magnetoplasmadynamics (MPD) thruster has been improved by increasing a discharge current was increased from 20 A to 60 A using a lanthanum hexaboride (LaB6) hollow cathode. The experimentally obtained thrust characteristics were consistent with that of electromagnetic acceleration. Using argon...

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. Boundary-layer separation on the compression surface could induce flow instability in pulsation and resonant modes. At subcritical operation, this flow insta...

Supersonic drag reduction performance using repetitive pulse energy depositions over blunt bodies was experimentally studied under two Mach numbers. The normalized drag reduction and energy deposition efficiency of Mach-1.92 over a 10-mm-dia. blunt-cylinder model were 8% and 1.2 at most, respectively. On the other hand, these values at Mach-3.20 ov...

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...

The behavior of a blast wave, in which an initial positive overpressure pulse is followed by a negative overpressure phase, has been investigated mainly by field test using such an explosive as trinitrotoluene (TNT) [1, 2]. The typical pressure history of a blast wave is shown in Fig. 1. The scaled distance Z, which is a function of released energy...

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.

In this study, we investigated the effects of the magnetic field profile near a ring anode on the ion acceleration characteristics of a diverging magnetic field electrostatic thruster. In an examined electrostatic thruster, a diverging magnetic field is applied in the ion acceleration region, which comprises a ring anode and an insulating plate in...

In this study, the effectiveness of repetitive laser pulse energy deposition over a double-cone model in a Mach 1.92 flow (half-apex angles of 22 and 40 deg) was investigated experimentally. The Reynolds number, based on the model’s outer diameter, was 3×105. Because of the shock wave/boundary-layer interaction, the shock wave over the cone’s trans...

The ablation spot area and impulse characteristics of various polymers were experimentally investigated against burst irradiation of Nd: YLF laser pulses with a pulse repetition frequency of 1 kHz, wavelength of 1047 nm, temporal pulse width of 10 ns, and single-pulse fluence of 6.1 J/cm² to 17.1 J/cm². The dependences of ablation area on the pulse...

The effects of a radio-frequency (RF) power on the ion generation and electrostatic acceleration in a helicon electrostatic thruster were investigated with a constant discharge voltage of 300 V using argon as the working gas at a flow rate either of 0.5 Aeq (Ampere equivalent) or 1.0 Aeq. A RF power that was even smaller than a direct-current (DC)...

Ion acceleration through a slowly diverging magnetic nozzle between a ring anode and a hollow cathode set on the axis of symmetry has been realized. Xenon was supplied as the propellant gas from an annular slit along the inner surface of the ring anode so that it was ionized near the anode, and the applied electric potential was efficiently transfo...

In this paper, applied-field magnetoplasmadynamic thrusters were operated with a discharge current lower than 20 A and an argon propellant flow rate under 4.0 mg / s by using a thermionic electron emission-type hollow cathode. Both axisymmetric and rectangular channel configurations were examined. The characteristic value of the ratio of the applie...

Electrostatic ion acceleration across a diverging magnetic field, which is generated by a solenoid coil, permanent magnets, and a yoke between an upstream ring anode and a downstream off-axis hollow cathode, is investigated. The cathode is set in an almost magnetic-field-free region surrounded by a cusp. Inside the ring anode, an insulating wall is...

The impact of a thermal bubble produced by energy deposition on the near-field pressure over a Mach 1.7 free-flight model was experimentally investigated using an aeroballistic range. A laser pulse from a transversely excited atmospheric (TEA) CO2 laser was sent into a test chamber with 68 kPa ambient pressure, focused 10 mm below the flight path o...

The effect of repetitive energy deposition on low Strouhal number oscillations of the shock wave induced by boundary-layer interaction over a cylinder-flare model was studied. The fluctuation of the energy deposition frequency was induced in the flow, because the bubble generated by the energy deposition flowed downstream along the surface repeated...

The ion beam energy performance in a helicon electrostatic thruster with various anode geometries was investigated. For discharge voltages from 100 to 300 V, the ion beam energy increased almost linearly with the discharge voltage. The rate of increase strongly depended on the anode inner diameter (ID). However, the ion beam energy was fit to a sin...

An experimental investigation of the interaction between a quasi-planar blast wave generated by 0.5 g report composition and a counter-Turbulent flow was conducted in a square field having an area of 20 x 15 m2. In the experiments, overpressure waveforms of the blast waves were measured using four microphones for both the cases without flow and wit...

A ring-force balance system for a supersonic wind tunnel with a small test section was developed. This force balance system can measure an applied force independently by measuring the strain on the ring part. A theoretical analysis of this system was conducted under three conditions: an infinitesimally thin ring-force balance, a ring-force balance...

The effect of the shock wave propagation Mach number and the discharged power on the shock wave modulation due to the discharged plasma was investigated experimentally. The shock wave acceleration and the shock wave attenuation was suggested with increasing the shock Mach number and the discharge power. In order to improve the measurement accuracy,...

A “counter-driver” shock tube was developed. In this device, two counter drivers are actuated with an appropriate delay time to generate the interaction between a shock wave and a flow in the opposite direction which is induced by another shock wave. The conditions for the counter drivers can be set independently. Each driver is activated by a sepa...

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 approximat...

The effectiveness of a "staged aftbody" proposed by Toyoda et al. (AIAA J., Vol. 52, 2014, pp. 2899-2901) was further investigated using an aeroballistic range with a free-flight Mach number of 1.7. Near-field pressure signatures were obtained from a pressure transducer that was flush-mounted on a flat plate. From these signatures, far-field pressu...

The relationship between impulse and crater formation on an Al ablator with repetitive irradiation of Nd:YAG laser pulses (wavelength of 1064 nm, pulse duration of 7 ns) is investigated. The mNs level impulse is measured in a vacuum by a torsion type impulse balance. Surface area changes caused by crater deepening are measured with a laser microsco...

In Japan, many research activities on electric propulsion and its accompanying science / technology have been executing for the near / far future space propulsion system by universities, institutes, manufacturers and JAXA. After the impressive and emotional return of “HAYABUSA” to earth, many studies on next generation of electric / plasma propulsi...

A steady-state, applied-field, rectangular magnetoplasmadynamics (MPD) thruster with permanent magnets has been developed. The thrust and discharge voltage were measured by varying propellant mass flow rates, discharge current and inter-electrode distance. Argon was used as the basic propellant. The effective energy consumption rates were evaluated...

Interaction between a shock wave and turbulence can yield complementary impacts to each other; when a shock wave is attenuated in turbulence the turbulent flow can gain energy from the shock wave, and vice versa

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

Two-wavelength laser interferometrymethod is commonly used to visualize an ionized gas flow.

The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent m...

The impulse characteristics of an aluminum ablator against repetitive Nd:YLF laser pulses with a 1047 nm wavelength and 5 to 15 ns pulsewidth were investigated. The laser was operated in burst mode varying the pulse repetition frequency, single-pulse energy, and number of pulses in a burst. The burst was repeated until the impulse reached saturatio...

Interaction of unsteady shock wave and Karman's vortex is experimentally investigated in a wind tunnel. Karman's vortex is generated behind a cylindrical bar and the Reynolds number based on the mean velocity and the cylinder diameter is set to 849. A spherical shock wave is emanated from an open end of a shock tube installed far downstream of the...

The interaction phenomena between the shock wave and the plasma was experimentally investigated. Due to the interaction, the shock wave deformation and attenuation were observed. And, the result suggested that the shock wave modulation effects became more significant with increasing shock Mach number. This tendency was also observed in one-dimensio...

When a shock wave ejected from the exit of a 5.4-mm inner diameter, stainless steel tube propagated through grid turbulence across a distance of 215 mm, which is 5–15 times larger than its integral length scale \(L_{u}\) , and was normally incident onto a flat surface; the peak value of post-shock overpressure, \(\Delta P_{\mathrm{peak}}\) , at...

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 separati...

The effectiveness of repetitive laser pulses energy deposition on the control the interaction between a shock wave and a boundary layer over a hemisphere-cylinder-flare model using is investigated. With symmetrical energy deposition, the flow separation was suppressed with the energy deposition, and decreasing the pressure loss over the flare. The...

Drag reduction performance over a blunt-body by a combination of a conical spike and repetitive energy depositions is investigated. Experiments are conducted in a Mach 2 supersonic flow in an in-draft wind tunnel, varying the length and the apex angle of the spike on a flat head body and the repetitive frequency of laser pulse energy depositions fr...

The decay characteristics and invariants of grid turbulence were investigated by means of laboratory experiments conducted in a wind tunnel. A turbulence-generating grid was installed at the entrance of the test section for generating nearly isotropic turbulence. Five grids (square bars of mesh sizes M = 15, 25 and 50 mm and cylindrical bars of mes...

In order to comprehend the interaction phenomena between plasma and shock wave, shock tube experiment and numerical analysis were conducted. From the Schrielen visualization result, the shock wave deformation as like branch like structure was observed. From the numerical simulation, it was clearly showed that the brunch liked deformation structure...