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Correct option is (B) flow past a half body

The best explanation: When a uniform of velocity U combines with a source flow of STRENGTH q, the RESULTANT flow is a flow over a half body.

The correct choice is (a) sum of STREAM FUNCTION of uniform flow and doublet flow

To explain: The stream for the resultant flow can be given by the sum of stream function of uniform flow and doublet flow. Here we need to consider CYLINDRICAL coordinates. MATHEMATICALLY,

Ψ = U*y + ((-u/2*pi*r)*sin θ.

The correct option is (a) SINK flow

The BEST I can explain: The flow in which the streamlines are DIRECTED towards the ORIGIN is called as sink flow. The sink flow is simply the negative of source flow. The streamlines vary inversely with the distance that is as the distance decreases the VELOCITY increases.

Correct option is (a) HIGHER

For EXPLANATION I would say: On the top of the CYLINDER usual non-spinning flow this EXTRA velocity contribution creates a higher than usual velocity at the top of the cylinder and a lower than usual velocity at the bottom. These velocities are assumed to be just outside the viscous boundary layer on the surface from Bernoulli’s EQUATION.

The CORRECT option is (b) surface tension

For EXPLANATION I would say: The surface tension is the property of a fluid which occurs because of the cohesive force between the molecules of the fluid. In a jet of oil, the molecules of oil and the air interact and also the molecules of the oil TRY to ACQUIRE the minimum AREA.

The correct OPTION is (B) False

The best explanation: In real life, zero drag is not acceptable because we know that drag is produced due to viscous effects which generate frictional shear stress at the BODY surface and which cause the flow to separate from the surface on the back of the body and thus large wake downstream is CREATED destroying the symmetry of the flow.

Right choice is (b) BUOYANCY

Best EXPLANATION: When a body is immersed in a fluid, an upward fluid is EXERTED by the fluid on the body. This upward force is EQUAL to the weight of the fluid DISPLACED by the body and is called as buoyancy or the force of buoyancy.

The correct option is (a) 2D flow

To elaborate: STREAM function are applicable only for 2D flow. It is DENOTED by PSI (Ψ). For a STEADY state flow, it is GIVEN by- Ψ=f(x,y), such that

δΨ/δx=v andδΨ/δy=u.

Correct option is (a) True

The BEST I can explain: The DIRECTION of the outward unit normal vector is POSITIVE when directed away from the body and it is carried out in the denominator at a singular point arises on the ITH panel because the control point itself can be the contribution to the j=1 panel.

Right answer is (d) SPINNING cylinder

Easy explanation: A FINITE lift is measured for the spinning cylinder in the wind tunnel.T he friction between the FLUID and the surface of the cylinder tends to drag the fluid NEAR the surface in the same direction as the rotational motion.

Right option is (c) IRROTATIONAL

To explain: VORTEX FLOW is irrotational everywhere except at the point r=0, where the VORTICITY is infinite. Therefore, the origin, r=0, is a singular point in the flow field. Here, the origin point REPRESENTS the singularity point.

Correct answer is (c) RANKINE OVAL of equal axes

To explain I would say: The flow past CYLINDER is called a Rankine oval of equal axes as it was discovered by Rankine and also the flow parameters on the upper and LOWER surface of the doublet flow REMAINS the same.

Right option is (b) velocity potential function

The EXPLANATION: Velocity function is the scalar function of space and TIME such that its negative derivative with RESPECT to any direction gives the fluid velocity in that direction. It is defined by phi (ϕ). Mathematically, it is given by, ϕ= f(X,y,z).

Right answer is (c) Joint effect of camber

The best I can explain: ROTATING flow is induced by the joint effect of camber, angle of attack and sharp trailing edge of the airfoil and should not be confused with a vortex LIKE a tornado encircling the CYLINDER or wing of an airplane in FLIGHT.

The correct choice is (a) The pressure difference between upstream and downstream direction of flow

For explanation I would say: A circular cylinder PRODUCES large DRAG due to the pressure difference between upstream and downstream of the flow. The difference in pressure is causes by the periodic separation of flow over the SURFACE of the cylinder. This will INCREASE the drag in the cylinder.

The correct choice is (c) stream function

For EXPLANATION I would say: Stream function is defined as the scalar function of SPACE and time such that its partial derivative with respect to any direction gives the velocity COMPONENT at right ANGLES to that direction. It is valid only for 2D flow and is denoted by Ψ.

Right answer is (a) to find a numerical METHOD

Explanation: The PURPOSE of non-lifting flow over an arbitrary bodies is to find a numerical method for appropriate solution on a high SPEED digital computer. The technique is CALLED the source panel. The numerical solution of potential flows by both source and vortex panel techniques has revolutionized the ANALYSES of low speed flows.

Right ANSWER is (d) equipotential LINE

The best explanation: The line ALONG which the velocity potential (Φ) is constant is called a equipotential line. For an equipotential line,

Φ=constant and also dΦ=0

The slope for the equipotential line can be given as=dy/dx.

The correct answer is (a) mass to volume

Best explanation: DENSITY is the ratio of mass to volume and is measured in kilograms per meters cube. The density of the liquids REMAINS CONSTANT while the density of gases changes with the variation of pressure and TEMPERATURE.

The correct option is (a) SINGULAR point

To explain: For a source flow, DIVERGENCE of velocity is ZERO everywhere expect at the origin where it is infinite. Thus, the origin is a singular point and we can INTERPRET this singular point as a discrete source or sink of a given strength, with a corresponding induced flow field about the point.

The correct answer is (d) u = -δϕ/δx, v = -δϕ/δy, w = -δϕ/δx

Explanation: Velocity POTENTIAL FUNCTION is scalar function of space and time and its negative derivative with respect to any direction GIVES the fluid velocity in that direction. MATHEMATICALLY, it is ϕ = f(x,y,z) such that,

u = -ϕδ/xδ,

v = -ϕδ/δy,

w = -ϕδ/δx.

The correct ANSWER is (c) steady uniform flow

To elaborate: The flow in which the flow parameters do not change with RESPECT to time is CALLED a steady uniform flow. The steadiness and uniformity need not occur TOGETHER. The flow particles move in a line with constant velocity.

Correct option is (a) Principle of moments

To explain I would say: The CENTRE of pressure can be CALCULATED using a principle of moments which STATES that the MOMENT of the resultant force about an axis is EQUAL to the sum of moments of the components about the same axis.

The correct choice is (a) two-dimensional flow around an AIRFOIL

Best explanation: Kutta-Joukowski theorem refers to Two-Dimensional flow around an airfoil and DETERMINES the lift generated by one unit of a span. Kutta-Joukowski theorem is an inviscid theory, but it is a good approximation for REAL viscous flow in typical aerodynamic APPLICATIONS.

The CORRECT answer is (d) sonic boom

The explanation: The sound which is related to shock WAVES that are created by the object travelling faster than the speed of sound is called a sonic boom. When an AIRCRAFT travels with a HIGH speed, series of pressure waves are also created and these when combine together leads to sonic boom.

Correct answer is (a) Irrotational

Easiest EXPLANATION: The flow outside the airfoil is irrotational and the circulation around any CLOSED curve not ENCLOSING airfoil is consequently zero. When the boundary layer separates, its displacement THICKNESS increases sharply, which modifies the outside potential flow and pressure field.

Correct option is (c) doublet

Best explanation: Doublet is the special case of source and sink with equal strength. LET q and -q be the strength of source and sink RESPECTIVELY. Let 2a be the DISTANCE between the source and sink and it approaches ZERO. The product 2a*q is called as doublet strength.

Correct OPTION is (b) irrotational

Explanation: When the rotational components are ZERO, it means that the flow travels in a LINEAR direction and the velocity POTENTIAL gives the direction of FLUID velocity in a particular direction. In irrotational flow, the velocity of the fluid travels in a linear direction.

Right option is (b) Uniform flow

To explain I WOULD SAY: Uniform flow is the one in which each particle in the flow moves in a line with a constant speed. Also, in uniform flow, the flow parameters do not CHANGE from TIME to time. They REMAIN constant throughout the flow.

Correct ANSWER is (a) True

Best explanation: By INTEGRATING from a to bthe complete velocity potential is obtained at POINT p and it can change from position to NEGATIVE along the sheet, that is the source sheet is REALLY a combination of line source and line sinks.

The correct option is (a) False

Easiest EXPLANATION: The shape of an arbitrary body depends on the distribution of singularities which in combination with a UNIFORM STREAM, produce the flow over the given body.T he purpose of this ELEMENTARY flow is to present such a direct method, limited for the present to non-lifting flows.

Correct choice is (a) Line integral around a closed loop enclosing the AIRFOIL

Explanation: Circulation is DEFINED as the line integral around a closed loop enclosing the airfoil of the component of the velocity of the FLUID tangent to the loop. To calculate the force on an airfoil, outside the boundary layer the vorticity is zero, everywhere the circulation is the same around every CIRCUIT.

Right ANSWER is (c) Roughened surfaces

To explain I WOULD SAY: To REDUCE the amount of drag on a CYLINDER various active and passive flow control method have been employed and tested successfully.T hese method include dimpled surfaces, trip wires, roughened surfaces.

Correct CHOICE is (b) HORIZONTAL LINE

To explain: The SHAPE of the Rankine oval of equal axes can be given by substituting the stream function as zero in the equation Ψ = U*y + ((-u/2*pi*r)*sin θ. When sin θ=0, θ=0, then a horizontal line through the origin of the DOUBLET is formed and it is x-axis.

Right option is (a) Smoke flow visualization

The explanation is: The visualization technique such as smoke flow visualization, surface oil film technique, particle image velocimetry have been EMPLOYED to LOCATE the position of transition and SEPARATION of a BOUNDARY LAYER.

The correct option is (a) FLOW past a CIRCULAR CYLINDER

To explain: In the above figure, the first diagram shows the uniform flow whereas, the second one shows the doublet flow (SOURCE sink combination of equal strength). The combination of these two leads to the flow past a cylinder.

Right choice is (a) 48%

To explain I would say: A 48% DRAG reduction of a cylinder by installing a much smaller cylinder in the UPSTREAM direction of flow. The shear LAYER coming from the smaller cylinder CHANGES the pressure DISTRIBUTION around the layer cylinder in such a way that the drag is dramatically altered.

Correct choice is (a) Sum of the freestream

Easy explanation: The normal component of the flow VELOCITY at the RTH control point is the sum of that due to the FREE stream and that due to the SOURCE panels. The boundary condition stats that this sum must be zero and it is the cruse of the source panel METHOD.

Correct CHOICE is (C) Smoke FLOW VISUALIZATION

For explanation: Smoke flow visualization has been used by bakic and peric to visualize the delayed separation of the flow over a smooth sphere. The flow separation occurs when the boundary layer TRAVELS far enough against an adverse pressure gradient.

Correct CHOICE is (a) It allows it to varies from one PANEL to next panel

Best EXPLANATION: The source strength ‘X’ per unit length be constant over a GIVEN panel but allow it to vary from one panel to the next, that if there are total n panel. The source panel strength per unit length is ‘Xn’. Therefore boundary condition is IMPOSED numerically by defining the midpoint of each panel.

The correct answer is (b) True

Best explanation: The NUMERICAL method for an appropriate solution on HIGH speed digital COMPUTER. This technique is CALLED source panel method, which, since the late 1960’s, has become a standard aerodynamic TOOL in industry and most research laboratories.