Correct Answer : liquid and gas
Explanation : When force is applied to liquid and gas, there will be an increasing deformation, proportional to the rate of change of deformation. Also, the molecules in liquid and gas are loosely packed. When filled in a container, they take the shape of that container.
Correct Answer : fluids
Explanation : Because fluid (liquid and gas) is a “squishy” substance. While the solid body is geometrically well defined and hence its motion can be defined easily. Whereas, in fluids, it is difficult to decide the qualitatively model the motion of the fluid.
Correct Answer : free molecular flow
Explanation : In free molecular flow, the gas molecules are spaced so far apart that collisions with the body surface occur only infrequently and the body surface can feel distinctly each molecular impact which reduces the vibration in the space vehicle.
Correct Answer : Pressure and density
Explanation : Both pressure and density vary from one point to another. Pressure and density vary with the altitude and are directly proportional to each other. Pressure and density does depend on a path as they change from one point to other. If one parameter is changed, it affects pressure and density.
Correct Answer : pressure and shear stress
Explanation : Pressure force and shear stress acts on the complete surface of the body which means that the surface force acts on the surface and not on a point or the body. Surface forces may act either on external or on an internal surface of the body.
Correct Answer : supersonic flow
Explanation : Supersonic flows are characterized by the presence of shock waves across which the flow properties and streamlines change discontinuously. In supersonic flow, the gas can be compressed using shock waves.
Correct Answer : inviscid flow
Explanation : The flow without friction, thermal conduction, or diffusion is practically impossible. During any process or flow, the energy losses take place which leads to frictional losses, thermal losses, diffusion and various other losses.
Correct Answer : Bernoulli's principle
Explanation : Bernoulli’s principle states that the sum of all the forms of energy (potential energy, kinetic energy, internal energy) remains constant. Only the weight of the body and the pressure forces act on the body.
Correct Answer : Inertia force to viscous force
Explanation : Reynold’s number is given by Re = VL ρ / μ, which signifies the inertia to viscous force occurring in a flow. ρ / μ is called as kinematic viscosity of the fluid. Larger Reynold’s number, greater will be the inertial effects.
Correct Answer : All the three models can be used based on the need
Explanation : The finite control volume considers a finite volume which may be either fixed in space or moving along a fluid. The infinitesimal small element considers a finite element which may be either fixed or moving along with the flow. The molecular approach is a microscopic approach and can be applied to atoms and molecules.
Correct Answer : Geometric Similarity
Explanation : Geometric similarity occurs when the model and prototype have same dimensional ratio in each direction. These ratios are called as scale ratio. For ex, Length scale ratio Lr = Lm/Lp where, m and p represent model and prototype.
Correct Answer : Dynamic Similarity
Explanation : For a dynamic similarity, the model and prototype must be geometrically and kinematically similar along with the condition of total sum of forces acting at a point on model and prototype must be equal. Inertia force satisfies the condition and hence it falls under dynamic similarity.
Correct Answer : Surface tension
Explanation : In a jet of oil, the molecules at the surface and the free layer differs because of which the oil resists the external force. The cohesive nature of the oil molecules helps to increase the surface area of the oil.
Correct Answer : Water
Explanation : The fluids which obey Newton’s law of viscosity are Newtonian fluids. It states that the applied shear stress is directly proportional to the amount of deformation.τ = μdv/dyWhere, μ—–viscosity of the fluidτ—-shear stressdv/dy -velocity gradient.
Correct Answer : Mass conservation
Explanation : Continuity equation is related to mass conservation. It states that the total mass entering a body is equal to the total mass leaving a body.Mass entering the body = mass leaving the body.
Correct Answer : Flux
Explanation : Flux is also referred to as flux density. It is the amount of quantity (q) which is flowing per unit volume(v). The quantity should have the ability to move or flow.
Correct Answer : Charge conservation
Explanation : In electromagnetic theory, charge conservation is a result of Maxwell’s equation which states that divergence of current density is equal to the negative rate of change of charge density.∇.J=- ρ/tWhere J-current density and ρ-charge density.
Correct Answer : volume continuity equation
Explanation : ∇.u=0 – In this equation, u is flow velocity and it states that the divergence of flow velocity is zero. Since the flow is incompressible, the density remains constant and thus the volume cannot be changed.
Correct Answer : ρ/t + ∇.(ρV)=0
Explaination : ρ-density V-velocity vector t-timeThe divergence represents the inflow and outflow whereas the time derivative represents the accumulation of mass inside a body. It states that the amount of mass entering the body is equal to the amount of mass leaving the body.
Correct Answer : Continuity equation
Explanation : Continuity equation is based on the conservation of mass. According to this law, for any system, the amount of mass always remains constant unless and until the mass is added or removed from the system. This means that the quantity of matter does not change.
Correct Answer : hydrostatic equation
Explanation : dp = -g ρ dy represents the hydrostatic equation where p is pressure acting on a body, g is acceleration due to gravity, dy is changed in vertical height. The net force on the element acts only in the vertical direction. The pressure force on the front and back faces are equal and opposite and hence cancel.
Correct Answer : First law of thermodynamics
Explanation : First law of thermodynamics states that energy can neither be created nor be destroyed but it can be converted from one form to another.
Correct Answer : KE = 0.5*m*v²
Explanation : It is product of mass and square of velocity. Kinetic energy comes in picture in case of moving objects and also for the objects which has certain mass. It is defined as the work needed to accelerate a body from its rest to the moving condition.
Correct Answer : Kinetic energy
Explanation : A moving object always has kinetic energy. When a body will move in a forward direction, it will gain some kinetic energy which will be the product of mass and square of velocity. A body in motion always store kinetic energy in it.
Correct Answer : Joules
Explanation : The formula for kinetic energy is 0.5*m*v². The dimensional formula for kinetic energy is kg*(m/s)², which may be defined as 1 joule. 1 joule = kg*m²/s². 1 Joule is defined as the energy transferred to an object when the force of 1 Newton is acted on a body through a distance of 1 meter.
Correct Answer : 900000 Joules
Explanation : KE=0.5*m*v².Substitute the values in the formula.Here, m=90 kg and v= 200 m/s.On solving the above equation we get,KE=0.5*90*(200)²= 900000 Joules.
Correct Answer : Enthalpy
Explanation : Enthalpy is the total heat content in the system. It is an extensive property and is the sum of internal energy plus the product of pressure and volume.H = U+ p*V
Correct Answer : Kinetic energy + potential energy + pressure energy
Explanation : The total energy is the sum of kinetic energy plus potential energy plus internal energy. Where kinetic energy is given by 0.5 m*v2 where m is the mass and v is the velocity. Potential energy is given by PE=mgh where, m is the mass, g is the acceleration due to gravity and h is the height. The internal energy is denoted by ‘I’.
Correct Answer : Streakline
Explanation : Streakline is defined as the locus of the particle that has earlier passed through the fixed point. In the case of the chimney, the chimney is the fixed point and the smoke which passes through it makes the locus. The path of the smoke can be traced.
Correct Answer : Streamline and pathline
Explanation : Both Streamlines and pathline are imaginary because streamline represents the direction of the fluid flow from a particular point in the fluid flow domain. This point can be anywhere in the fluid domain and is imaginary. Pathline is the path traced by a fluid element at a given interval of the time.
Correct Answer : stream surface
Explanation : If a curve, line or closed curve is used as a start point then the streamlines so obtained are called a stream surface. In this case, Stream function comes into the picture which defines the scalar function of these streamlines.
Correct Answer : Mass
Explanation : Mass is not related to the streamlines because the velocity does not have normal component, it flows in a straight direction and does not have any normal components either and hence, the mass cannot cross the streamline.
Correct Answer : x=y
Explanation : In steady flow, the velocity does not change with respect to time. Hence, the velocity remains constant that is dy/dx=y/x. On integrating the above equation we get, x=y, which proves that pathline and streamline are same for steady flow with same velocity field.
Correct Answer : y=xt
Explaination : Consider the velocity vector, V= xi +y*tjHere u=x and v=y*tWe know that dx/u=dy/v=dz/wOn substituting the vales and integrating, we get, y=xt.
Correct Answer : Angular velocity
Explanation : Angular velocity comes in the picture when the flow is rotational that is the flow which has both translational as well as rotational motion. It is the rate of change of angular displacement. It is denoted by omega and its SI unit id radian per second.
Correct Answer : ω = 0.5(dθ1/dt + dθ2/dt)
Explaination : Angular velocity is defined as the average of the angular velocities of the lines (2D or 3D). This is the case of 2D flow. Consider a flow, let dθ1/dt be the x component of velocity and dθ2/dt be the y component of velocity.
Correct Answer : Vorticity
Explaination : Vorticity is twice the angular velocity. The angular velocity of the fluid plays an important role in theoretical aerodynamics and 2*ω occurs frequently and in order to reduce the complexity, we use vorticity.
Correct Answer : vorticity
Explanation : The curl of velocity and the vorticity for a 3D flow is the same. Therefore, the curl of velocity equals to the vorticity of the 3D flow element. The equation can be defined by 2*ω = ∇*V where ∇*V – curl of velocity and 2*ω is the vorticity.
Correct Answer : rotational
Explaination : In rotational flow, the fluid element has a finite angular velocity which means the element can undergo rotation and as well as distortion. The amount of distortion depends on the velocity field.
Correct Answer : irrotational
Explaination : In irrotational flow, the fluid element does not have a finite angular velocity which means the element cannot undergo rotation and as well as distortion. The motion of the fluid element is purely translational motion.
Explanation : The absence of vorticity means the flow is irrotational flow, which simplifies the flow analysis. This is greatly used in case of inviscid flows. The flow analysis becomes easy for irrotational flow since there is no rotational motion of the fluid element.
Explanation : For the subsonic flow over an airfoil, the flow is irrotational which means the motion of the fluid element is translational. In such cases, a thin boundary layer is formed around the surface. In this boundary layer, the flow is highly rotational whereas, outside the boundary layer it is irrotational.
Correct Answer : Circulation
Explanation : Circulation is the line integral of the velocity around a closed curve in the flow. It depends on the velocity field and the selection of the curve. It defines the movement of the flow inside the curve. It is given by-Γ=?c V. ds where, Γ- circulation, ?c – curve, V.ds – velocity field.
Correct Answer : zero
Explanation : In the case of irrotational flow, the circulation about a curve is equal to the vorticity integrated over any open surface bounded by the curve. This leads to the result that if the flow is irrotational everywhere, the circulation is zero.
Correct Answer : negative of circulation per unit area
Explanation : The relation between circulation and vorticity can be given by-(∇*V).n = -dΓ/dSWhere dS – infinitesimal area enclosedC – Infinitesimal curve.
Correct Answer : divergence of velocity
Explanation : Using Stoke’s theorem, the line integral of velocity field along a closed curve is equal to the surface integral of velocity field along a closed path normal to the area covered by the path. But we know that curl of velocity is called vorticity and hence, the circulation is called a flux of vorticity.
Correct Answer : Honey
Explanation : Honey has more viscosity. Viscosity is the measure of the resistance offered by the flow to the shear or tensile stress. The relative motion between the two surfaces moving with different velocities is given by viscosity.
Correct Answer : boundary of an object
Explanation : The boundary layer is formed at the boundary of an object. The boundary layer divides the flow into two parts- Viscous and inviscid. The flow inside the boundary layer is highly viscous whereas, the flow outside the boundary is inviscid flow.
Correct Answer : scalar
Explanation : In a macroscopic view, circulation is a scalar quantity as it is defined as the line integral of velocity field over a closed region. In a microscopic view, circulation is a flux of vorticity, which makes it a vector quantity.
Correct Answer : Reynold’s number
Explanation : The nature of the boundary layer depends on Reynold’s number which is the ratio of inertial force to viscous force. Depending on the value of Reynold’s number, the boundary layer may be laminar (the flow is continuous) or it may be turbulent ( the flow is discontinuous).
