Abstract:The reflection of rightward moving shocks (RMSs) belonging to the first and second families, over an initially steady oblique shock wave (SOSW) produced by a wedge, is studied in this paper. Various possible combinations of primary reflection (reflection at the intersection point of the RMS and the SOSW) and secondary reflection (reflection, on the wedge, of reflected shock waves of the primary reflection) are identified and the transition conditions are studied. For an RMS of the first family, the shock refle… Show more
“…On the right of the RMOS the flow is horizontal, so . The situation considered by Wang & Wu (2022) corresponds to (and ). Figure 1.Initial state of the reflection between an oblique RMS and a steady oblique shock wave attached to a sharp wedge ( a ) with ( b ) with .…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…In order to consider the influence of , we determine the flow parameters in region from those in region . The Mach number and the shock speed are the other two input parameters as considered before by Wang & Wu (2022).…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…As in Wang & Wu (2022), the computation is performed with two steps. First, the steady solution without the RMS is calculated.…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…(2020), who also considered an incident shock of the first family. Recently, Wang & Wu (2022) considered a rightward-moving normal shock of both first and second families. For an RMS of the first family, they used frame transformation to show that the shock reflection problem is equivalent to a shock interference problem, so we may have the type I, II, IV, V and VI shock interferences of Edney (1968).…”
Section: Introductionmentioning
confidence: 99%
“…In this paper, the study of transition conditions by Wang & Wu (2022) for the case of a normal RMS of the first family over a steady oblique shock is extended to the case of an oblique RMS.…”
The reflection of a rightward-moving oblique shock (RMOS) belonging to the first family, over an initially steady oblique shock wave (SOSW) produced by a wedge, is studied in this paper. To cover all possibilities, the problem is divided into a pre-shock reflection problem, for which the incident shock is assumed to reflect over the pre-interaction part of the SOSW, and a post-shock reflection problem, for which the incident shock is assumed to reflect over the post-interaction part. Such division, together with the definition of the equivalent problem defined on the reference frame co-moving with the nominal intersection point of the two shock waves, allows us to connect the reflection patterns with the six types of shock interference of Edney, which include type I–VI shock interferences depending on how an upstream oblique shock intersects a bow shock (types I and II are regular and Mach reflections of two shocks from the opposite sides; type III and type IV have two triple points or two Mach reflection configuration; type V and type VI are irregular and regular reflections of two shocks from the same side). We are thus able to identify all possible shock reflection types and find their transition conditions. Pre-shock reflection may yield IV, V and VI (of Edney's six types) shock interferences and post-shock reflection may yield I, II and III shock interferences. Pre- and post-shock reflections possibly occur at two different parts of the SOSW, and the complete reflection configuration may have one or both of them. Both transition condition study and numerical simulation are used to show how pre-shock reflection and post-shock reflection exist alone or coexist, leading to various types of combined pre-shock and post-shock reflections.
“…On the right of the RMOS the flow is horizontal, so . The situation considered by Wang & Wu (2022) corresponds to (and ). Figure 1.Initial state of the reflection between an oblique RMS and a steady oblique shock wave attached to a sharp wedge ( a ) with ( b ) with .…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…In order to consider the influence of , we determine the flow parameters in region from those in region . The Mach number and the shock speed are the other two input parameters as considered before by Wang & Wu (2022).…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…As in Wang & Wu (2022), the computation is performed with two steps. First, the steady solution without the RMS is calculated.…”
Section: Problem Set-up Observation Of Pre- and Post-shock Reflection...mentioning
confidence: 99%
“…(2020), who also considered an incident shock of the first family. Recently, Wang & Wu (2022) considered a rightward-moving normal shock of both first and second families. For an RMS of the first family, they used frame transformation to show that the shock reflection problem is equivalent to a shock interference problem, so we may have the type I, II, IV, V and VI shock interferences of Edney (1968).…”
Section: Introductionmentioning
confidence: 99%
“…In this paper, the study of transition conditions by Wang & Wu (2022) for the case of a normal RMS of the first family over a steady oblique shock is extended to the case of an oblique RMS.…”
The reflection of a rightward-moving oblique shock (RMOS) belonging to the first family, over an initially steady oblique shock wave (SOSW) produced by a wedge, is studied in this paper. To cover all possibilities, the problem is divided into a pre-shock reflection problem, for which the incident shock is assumed to reflect over the pre-interaction part of the SOSW, and a post-shock reflection problem, for which the incident shock is assumed to reflect over the post-interaction part. Such division, together with the definition of the equivalent problem defined on the reference frame co-moving with the nominal intersection point of the two shock waves, allows us to connect the reflection patterns with the six types of shock interference of Edney, which include type I–VI shock interferences depending on how an upstream oblique shock intersects a bow shock (types I and II are regular and Mach reflections of two shocks from the opposite sides; type III and type IV have two triple points or two Mach reflection configuration; type V and type VI are irregular and regular reflections of two shocks from the same side). We are thus able to identify all possible shock reflection types and find their transition conditions. Pre-shock reflection may yield IV, V and VI (of Edney's six types) shock interferences and post-shock reflection may yield I, II and III shock interferences. Pre- and post-shock reflections possibly occur at two different parts of the SOSW, and the complete reflection configuration may have one or both of them. Both transition condition study and numerical simulation are used to show how pre-shock reflection and post-shock reflection exist alone or coexist, leading to various types of combined pre-shock and post-shock reflections.
This paper explores the effects of an abrupt cross-section area change of gas pipes on the propagation law of explosion. For this, an explosion pipe experimental system was established, and a numerical research was conducted. By experimental and numerical simulation, the evolution of the overpressure, temperature, vorticity, and kinetic energy of shock waves of gas explosion in abrupt pipelines was investigated. This allowed us to obtain expressions for the attenuation coefficient, increase coefficient, and reflection coefficient of gas explosion overpressure. The study indicates that an abrupt increase of the pipeline cross-section area leads to a decrease of shock wave overpressure and vice versa. For a given change of cross-section area, the attenuation coefficient gradually increases as the initial peak overpressure rises, whereas the increase coefficient and reflection coefficient both present a decreasing trend. An abrupt change in the pipe structure can inhibit the propagation of gas explosion flames. The explosive gas is affected by the turbulence effect after passing through the middle large-diameter pipe, and the vorticity curve exhibits a clear peak. In addition, the large eddy motion caused by strong confinement increases the kinetic energy of the gas in pipes. The above research outcomes contribute to further enriching the basic theory of gas explosion for the study of gas explosion propagation in mining laneway.
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