Oblique Shock Wave

Definition

An oblique shock wave is a type of shock wave that occurs when a supersonic flow encounters an inclined surface, resulting in a sudden change in flow properties such as pressure, temperature, and velocity. Unlike normal shock waves, which are perpendicular to the flow direction, oblique shocks are angled and are typically found in situations like airfoils or nozzles where the flow is deflected. These shock waves can also lead to subsequent expansion fans that can alter the flow characteristics further downstream.

5 Must Know Facts For Your Next Test

1. Oblique shock waves are characterized by an increase in pressure and temperature while decreasing the velocity of the flow.
2. The angle of an oblique shock wave is dependent on the initial Mach number of the flow and the deflection angle of the surface it encounters.
3. When an oblique shock wave forms, it often results in a series of downstream expansion waves that can further affect the flow characteristics.
4. The study of oblique shock waves is essential in aerodynamics, particularly for the design of aircraft wings and supersonic nozzles.
5. Oblique shocks can exist at various angles, allowing for flexibility in design and efficiency in supersonic flight applications.

Review Questions

• How do oblique shock waves differ from normal shock waves in terms of their orientation and effects on flow properties?
  • Oblique shock waves differ from normal shock waves primarily in their orientation; oblique shocks are inclined relative to the flow direction while normal shocks are perpendicular. This difference affects how they alter flow properties. Oblique shocks result in a more gradual change in pressure and velocity, allowing for different configurations like airfoils to maintain performance at high speeds, while normal shocks cause an abrupt transition from supersonic to subsonic speeds.
• What role do oblique shock waves play in aerodynamic design and how do they influence the performance of airfoils?
  • Oblique shock waves are crucial in aerodynamic design as they help manage flow around surfaces at supersonic speeds. The presence of these shocks allows designers to optimize shapes, such as airfoil angles, to minimize drag and maximize lift. By controlling the angle of attack and understanding how these shocks interact with expansion waves, engineers can enhance the overall efficiency and performance of aircraft operating at high velocities.
• Evaluate how the interaction between oblique shock waves and expansion fans affects supersonic flow characteristics and overall efficiency.
  • The interaction between oblique shock waves and expansion fans significantly impacts supersonic flow characteristics by altering pressure and velocity profiles downstream. As oblique shocks increase pressure and temperature, subsequent expansion fans reduce these properties, creating a balance that can optimize flow efficiency. This complex interaction can be analyzed through computational fluid dynamics models, leading to innovative designs that improve performance while minimizing drag for high-speed aircraft.

Related terms

Normal Shock Wave: A normal shock wave is a shock wave that occurs when supersonic flow is abruptly decelerated to subsonic speeds, characterized by a perpendicular orientation to the flow direction.

Expansion Wave: An expansion wave is a phenomenon that occurs when a supersonic flow expands around a convex surface, leading to a decrease in pressure and density without the abrupt changes associated with shock waves.

Mach Number: The Mach number is the ratio of the speed of an object to the speed of sound in the surrounding medium, which is crucial for determining whether a flow is subsonic, transonic, or supersonic.