Oscillation Phenomena of Pseudo-Shock Waves

Ikui, Takefumi; Matsuo, Kazuyasu; Nagai, Minoru; Honjo, Masanobu

doi:10.1299/jsme1958.17.1278

Cited by 64 publications

(26 citation statements)

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“…This nature was observed early on by Ikui et al (1974b) and has continued to be the focus of studies more recently by Sugiyama et al (1988), Le et al (2008a,b), Tan et al (2009) andWagner et al (2009). Ikui et al (1974b) note that previous investigations into shocks trains were able to explain the time-mean static pressure distributions, however in reality the shock train oscillates about a mean position which results in fluctuations of the local static pressures. Ikui et al (1974b) found from their own shock train experiments that the amplitude of the fluctuations in pressure due to the oscillation could amount up to 60% of the total pressure difference across the entire shock train.…”

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 75%

“…Ikui et al (1974b) note that previous investigations into shocks trains were able to explain the time-mean static pressure distributions, however in reality the shock train oscillates about a mean position which results in fluctuations of the local static pressures. Ikui et al (1974b) found from their own shock train experiments that the amplitude of the fluctuations in pressure due to the oscillation could amount up to 60% of the total pressure difference across the entire shock train. They also found that the strength of the oscillation of the shock train scales with Mach number.…”

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 88%

“…They also found that the strength of the oscillation of the shock train scales with Mach number. Ikui et al (1974b) observed that the frequency of the oscillations depend on the geometry of the duct. From spectral density analysis of the data, they revealed that the oscillations of the shock trains in their tests had two prominent peaks of multiples of 10 Hz and 100-200Hz, which they note correspond to the Helmholtz resonance and the pipe resonance respectively.…”

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

“…From spectral density analysis of the data, they revealed that the oscillations of the shock trains in their tests had two prominent peaks of multiples of 10 Hz and 100-200Hz, which they note correspond to the Helmholtz resonance and the pipe resonance respectively. Ikui et al (1974b), using a one-dimensional model where Shock Train and Pseudo-Shock Experiments Section 2.1 25 the inflow was given a small perturbation, calculated the displacement of and pressure ratio across the shock train. The results from their calculations agree qualitatively with the amplitude of the oscillation of the shock train observed in their experiments.…”

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

“…The results from their calculations agree qualitatively with the amplitude of the oscillation of the shock train observed in their experiments. From this analysis, Ikui et al (1974b) propose that the oscillation of the shock train may be caused by the interaction of the shock train with small perturbations in the supersonic flow upstream of the shock train. Sugiyama et al (1988) investigated, using high-speed schlieren photography in conjunction with wall pressure measurements, the oscillatory nature of the two types of shock trains (λ and X types) commonly encountered.…”

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

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Investigation of pre-combustion shock trains in a sramjet using a shock tunnel at Mach 8 flight conditions

Ridings¹

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One of the major challenges to scramjet propulsion is the ability to operate over a wide range of Mach numbers. The dual-mode scramjet has the advantage that it can operate much like a ramjet at low Mach numbers, with subsonic flow entering the combustion chamber, and as a conventional scramjet at higher Mach numbers where the flow remains supersonic throughout the engine. A dual-mode scramjet is able to operate as a ramjet by allowing a shock train to form in the section between the inlet and combustor known as the isolator. This pre-combustion shock train, which is a series of intersecting shock and expansion waves, provides additional compression of the flow allowing subsonic flow to be supplied to the combustion chamber.Free-piston shock tunnels, such as Stalker Tubes, are typically used to test scramjet engines due to the high enthalpy flows which these facilities can produce. However these impulse type wind tunnels have short test times of the order of milliseconds. As the pre-combustion shock train involves large regions of separated flow, which take longer than attached flow to establish, there is some question as to whether dual mode can be modelled in Stalker Tubes.This work investigates whether pre-combustion shock trains can be studied in shock tunnels at the upper end of the dual-mode regime and if so, how this phenomenon affects scramjet performance. Experiments were conducted in the T4 Stalker Tube at The University of Queensland at a condition which represents flight at Mach 8 at an altitude of 26 km. This corresponds to a dynamic pressure of 105 kPa and a total enthalpy of 3.1 MJ kg −1 .The experiments were conducted using a simple axi-symmetric scramjet, which comprised a short inlet, an isolator, fuel injectors and three interchangeable combustion chambers. The set of combustion chambers consisted of a constant area and two divergent combustors with half-cone angles of 1 • and 2 • . The different combustion chambers were tested to assess the effect which area expansion has on the shock train and on the overall combustion efficiency of the engine. The model was arranged in a semi-direct connect configuration to produce the desired conditions at the isolator entrance. Gaseous hydrogen was used as the fuel and was injected via six port-hole injectors equally spaced around the circumference. Wall static pressures were measured along the isolator and combustor walls. A quasi-one-dimensional cycle analysis code, ii which is capable of modelling separated flow, is used to model the flow through the engine and provides estimates of the combustion efficiency and distribution of heat release.Robust combustion was observed in the experiments over a range of fuel equivalence ratios between 0.5 and 1.35, for all three combustor configurations. Results for the constant area combustor show that at an equivalence ratio approximately equal to 0.7 the boundary layer separates due to the pressure rise generated from combustion, forming a shock train upstream of fuel injection. With increasing equivalence...

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Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 75%

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 88%

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

Section: Oscillatory Nature Of Shock Trainsmentioning

confidence: 99%

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Investigation of pre-combustion shock trains in a sramjet using a shock tunnel at Mach 8 flight conditions

Ridings¹

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An immersed discontinuous Galerkin method for compressible Navier‐Stokes equations on unstructured meshes

Hong

Febrianto

Zhang

et al. 2019

Numerical Methods in Fluids

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Summary We introduce an immersed high‐order discontinuous Galerkin method for solving the compressible Navier‐Stokes equations on non–boundary‐fitted meshes. The flow equations are discretised with a mixed discontinuous Galerkin formulation and are advanced in time with an explicit time marching scheme. The discretisation meshes may contain simplicial (triangular or tetrahedral) elements of different sizes and need not be structured. On the discretisation mesh, the fluid domain boundary is represented with an implicit signed distance function. The cut‐elements partially covered by the solid domain are integrated after tessellation with the marching triangle or tetrahedra algorithms. Two alternative techniques are introduced to overcome the excessive stable time step restrictions imposed by cut‐elements. In the first approach, the cut‐basis functions are replaced with the extrapolated basis functions from the nearest largest element. In the second approach, the cut‐basis functions are simply scaled proportionally to the fraction of the cut‐element covered by the solid. To achieve high‐order accuracy, additional nodes are introduced on the element faces abutting the solid boundary. Subsequently, the faces are curved by projecting the introduced nodes to the boundary. The proposed approach is verified and validated with several two‐ and three‐dimensional subsonic and hypersonic low Reynolds number flow applications, including the flow over a cylinder, a space capsule, and an aerospace vehicle.

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