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Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE) PDF Download

Source or Sink

Source flow -

  • A flow with straight streamlines emerging from a point.

  • Velocity along each streamline varies inversely with distance from the point (shown in Fig. 20.3).

  •  Only the radial component of velocity is non-trivial. (vθ=0, vz=0 ).

 

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)

 

In a steady source flow the amount of fluid crossing any given cylindrical surface of radius r and unit length is constant Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)   

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                                                       (20.10a)

 

(which shows that velocity is inversely proportional to the distance )

where, K is the source strength        Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)    is the volume flow rate

The definition of stream function in cylindrical polar coordinate states that

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                    (20.11) 

For the source flow,

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                                           (20.13) 

Combining Eqs (20 .12) and (20.13) , we get

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                                         (20.14)

 

Thus  

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)

 

Because the flow is irrotational, we can write      

 

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                              (20.15)

 

The integration constants C1 and C2 in Eqs (20.14) and (20.15) have no effect on the basic structure of velocity and pressure in the flow.

The equations for streamlines and velocity potential lines for source flow become

 

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                                                   (20.16)
 

= source strength and is proportional to Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)
Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE) the rate of volume flow from the source per unit depth perpendicular to the page

 

Sink flow

  • When  Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE) is negative , we get sink flow,

  • here the flow is in the opposite direction of the source flow.


In Fig. 20.3, the point 0 is the origin of the radial streamlines. We visualize that point O is a point source or sink that induces radial flow in the neighbourhood .

The point source or sink is a point of singularity in the flow field (because vr becomes infinite).

  The stream function and velocity potential function are

Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE)                                      (20.17)                                                          

 

The document Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) | Additional Documents & Tests for Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Additional Documents & Tests for Civil Engineering (CE).
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FAQs on Analysis of Inviscid, Incompressible, Irrotational Flows (Part - 2) - Additional Documents & Tests for Civil Engineering (CE)

1. What are the assumptions made in analyzing inviscid, incompressible, irrotational flows?
Ans. The assumptions made in analyzing inviscid, incompressible, irrotational flows are that the flow is frictionless (inviscid), the fluid has a constant density (incompressible), and the fluid particles do not rotate (irrotational). These assumptions simplify the mathematical analysis of the flow and allow for the use of potential flow theory.
2. What is the significance of inviscid flow in civil engineering?
Ans. Inviscid flow is significant in civil engineering as it allows engineers to analyze and predict the behavior of fluids in various structures and systems. By neglecting the effects of viscosity, engineers can simplify calculations and make design decisions based on the assumption of frictionless flow. This is particularly useful in designing fluid transport systems, such as pipelines and channels, where minimizing energy loss due to friction is important.
3. How does the assumption of incompressibility affect the analysis of fluid flow?
Ans. The assumption of incompressibility means that the fluid density remains constant throughout the flow. This assumption simplifies the mathematical equations used to analyze fluid flow by eliminating the need to consider changes in density. Incompressible flow is often used in civil engineering for practical purposes, as many fluids, such as water, can be approximated as incompressible under normal conditions.
4. What is the significance of irrotational flow in civil engineering applications?
Ans. Irrotational flow is significant in civil engineering as it allows for the analysis of fluid flow without considering the rotational motion of fluid particles. This simplifies the mathematical analysis and enables engineers to make design decisions based on potential flow theory. Irrotational flow is commonly used in the analysis of open channel flow, hydraulic structures, and aerodynamics.
5. What are the limitations of assuming inviscid, incompressible, irrotational flows?
Ans. The assumptions of inviscid, incompressible, irrotational flows have certain limitations. In reality, all fluids have some degree of viscosity, which affects the flow behavior. Additionally, compressibility effects become significant at high speeds or in the presence of large pressure gradients. Finally, the assumption of irrotational flow may not hold true in cases where vortices or rotational motion are important, such as in turbulent flow or near solid boundaries. Therefore, while these assumptions are useful for certain engineering analyses, they may not accurately represent real-world flow conditions in all cases.
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