What Are Oblique Shock Waves and Expansion Waves?

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Discussion Overview

The discussion centers around the concepts of oblique shock waves and expansion waves, with participants seeking definitions and explanations related to these phenomena in the context of compressible flow and aerodynamics. The scope includes theoretical understanding and practical implications, particularly in relation to drag on aircraft.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant requests a simple definition of oblique shock waves and expansion waves.
  • Another participant expresses concern that the inquiry may be homework-related and suggests adherence to guidelines for homework help.
  • A participant clarifies that their inquiry is part of a research project for Year 12, indicating a need for external assistance due to lack of responses from industry contacts.
  • Reference is made to compressible flow textbooks, specifically mentioning works by Anderson and Oosthuizen.
  • A participant describes their understanding that an oblique shock wave occurs at an angle to the flow, resulting in increased density, pressure, and temperature, while also noting that downstream fluid flow speed decreases.
  • The same participant questions whether this increase in density and pressure contributes to increased drag on an aircraft by converting kinetic energy to thermal energy.
  • Another participant suggests looking up "wave drag" for additional information.
  • A later reply indicates that the participant found information on wave drag helpful.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definitions of oblique shock waves and expansion waves, and multiple viewpoints regarding the implications of these concepts on drag remain present.

Contextual Notes

Some limitations include potential missing assumptions about the definitions of shock and expansion waves, as well as the dependence on specific contexts within compressible flow theory. The discussion does not resolve the mathematical or theoretical complexities involved.

Who May Find This Useful

Readers interested in aerodynamics, compressible flow, or those engaged in high school or introductory university-level physics and engineering studies may find this discussion relevant.

fatlady1ac
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Would anybody be able to give me a simple definition on the question below.
Thanks Dylan

 What are oblique shock waves? What are expansion waves?
 
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This smells like homework, in which case we are not allowed to answer without you following the guidelines outlined in the homework section and showing that you have at least attempted the problem. Honestly, assuming this is homework, you can find this pretty quickly in your textbook... or on Google.
 
Its not necessarily homework, however I understand the guide rules, but I agree why it cannot be answered. It is actually a research project which I have to finish as part of my Year 12 which is anoyingly tedious. Anyway I need to have shown evidence that I have asked others for help, and the various people I have tried to talk to in the industry have not replied. Thus I thought I could ask a few questions on PF as part of my communication.
Thanks for the reply anyway I appreciate it.
 
Do you have a compressible flow book handy like Anderson or Oosthuizen (sp)?
 
a quick google or wiki search will tell you everything you need to know for casual research on the subject.
 
Yes I have a book written by John D. Anderson called Fundamentals of Aerodynamics.
From what I have studied is right to assume that a shock wave that occurs at a given angle to the flow is an oblique shock wave, and the fluid in the shock increases in density as it is compressed, resuting in greater pressure and temperature. So the fluid flow speed downstream is less.
Does the above directly increase the drag on an aircraft by converting some of the propulsive (kinetic energy) to thermal energy.
My research is directed into how to the speed of sound increases drag.
Thanks
 
Google wave drag. That ought to give you a little help.
 
Thanks for all the replies, I have subsequently looked at wave drag and it has been of help.
 

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