Shock Phenomena

 

 

 

If a fluid is moving at a rate above the speed of sound:

 

- the disturbance in the flow created by the object cannot be transmitted up stream

 

-the flow will not decelerate, thus creating a phenomenon known as “shock”, as the fluid collides with the object placed in its path.

 

 

 

-There are primarily two different kinds of shock:

1)    Normal and

2) Oblique

 

 

 

 

 

Normal Shock

 

 

                                             

         A normal shock is a shock flow perpendicular to fluid flow

causing a pressure rise and velocity decrease suddenly and irreversibly.

                     Governing Equations

 

 

 

 

 

 

Oblique Shock

 

 

       If a body is placed in the path of a fluid, a disturbance will be created due to the presence of that body.  If the body is wedge shaped, as in Figure 2-1(above), its presence in the fluid will be felt at different locations depending upon its position in the flow field.

 

      Thus, the fluid will navigate its way around the body at different points in time. In other words, the closer to the center of the flow field a molecule is, the sooner the presence of the body will be felt and the further a molecule is outside of the flow field, the later the body’s presence will be felt.

 

If the flow is considered to be moving with a velocity above the speed of sound, the shock-line that is created will be “oblique”.  Thus the flow will feel the shock line at some angle, q.  The angle (q) of the oblique shock is a direct function of the speed at which the flow is moving, and the angle of incline of the wedge placed in its path. 

 

Therefore, when a flow passes through an oblique shock it not only experiences a sudden and irreversible increase in pressure, temperature, and density and decrease in velocity.  The flow also experiences a sudden change in direction.

 

 

 

 

In-Depth Analysis

 

 

 

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