# Aerodynamics Questions and Answers – Circulation

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Circulation”.

**1. Circulation is referred to as _____________**

**a) divergence of velocity**

b) velocity field

c) flux of vorticity

d) velocity

**Explanation**: The line integral of a velocity field along a closed curve equals the surface integral of a velocity field along a closed path normal to the area covered by the path, according to Stoke’s theorem. However, we know that the curl of velocity is known as vorticity, and hence the circulation is known as a vorticity flux.

**2. Which of the following has more viscosity?**

a) Water

**b) Honey**

c) Oil

d) Juice

**Explanation:** Honey has a higher viscosity than sugar. The viscosity of a fluid is a measure of its resistance to shear or tensile stress. Viscosity determines the relative motion between two moving surfaces with differing velocities.

**3. The boundary layer is formed at the _____________**

**a) boundary of an object**

b) surface of an object

c) at a point on an object

d) edges of an object

**Explanation**: The boundary layer is created at the object’s edge. The viscous and inviscid sections of the flow are separated by the boundary layer. Inside the boundary layer, the flow is highly viscous, but beyond the boundary layer, the flow is inviscid.

**4. The nature of the boundary layer depends on _____________**

a) Mach number

b) Inertia force

**c) Reynold’s number**

d) Viscosity

**Explanation**: Reynold’s number, which is the ratio of inertial force to viscous force, determines the type of the boundary layer. The boundary layer can be laminar (continuous flow) or turbulent (turbulent flow) depending on the magnitude of Reynold’s number ( the flow is discontinuous).

**5. In microscopic view, Circulation is a __________ quantity.**

a) vector

b) dimension less

**c) scalar**

d) non-measurable

**Explanation:** Circulation is a scalar quantity in a macroscopic sense, as it is defined as the line integral of the velocity field across a closed region. Circulation is a flux of vorticity in a microscopic view, making it a vector quantity.

**6.The line integral of a closed curve around of a velocity field is defined as____________**

a) Vorticity

**b) Circulation**

c) Dilatation

d) Streamline

**Explanation**: The line integral of the velocity around a closed curve in the flow is called circulation. It is determined by the velocity field and the curve selection. It specifies how the flow moves within the curve. It is equal to c V. ds, where c is the curve and V.ds is the velocity field.

**7. If the flow is irrotational everywhere within the contour of integration then the circulation is ____________**

a) 1

b) positive

c) negative

**d) zero**

**Explanation:** The circulation around a curve in irrotational flow equals the vorticity integrated across any open surface limited by the curve. As a result, if the flow is irrotational in every direction, the circulation is zero.

**8. The component of vorticity normal to dS is equal to __________**

a) circulation per unit area

**b) negative of circulation per unit area**

c) zero

d) circulation

**Explanation**: The relation between circulation and vorticity can be given by-

(∇*V).n = -dΓ/dS

Where dS – infinitesimal area enclosed

C – Infinitesimal curve.

The systemic circulation ensures that all body tissues receive adequate blood supply. It transports oxygen and nutrients to the cells while also collecting carbon dioxide and trash. The left ventricle pumps oxygenated blood from the arteries to the capillaries in the body’s tissues, which is known as systemic circulation. The circulation around a curve in irrotational flow equals the vorticity integrated across any open surface limited by the curve. As a result, if the flow is irrotational in every direction, the circulation is zero.