Specific heat of polytropic process cn

Derive :- Specific heat of polytropic process cn = cv (gamma-n)/(1-n)

Space flight m.c.q for GATE Aerospace Engineering

1.     Geocentric orbits with altitudes up to 2,000 

(a)   Low Earth orbit (LEO)

(b)   Medium Earth orbit (MEO): 

(c)    Geostationary orbit (GEO)

(d)   Geosynchronous orbit (GSO)

2.      Pick the correct option:

[A] All geostationary orbits are also geosynchronous, but not all geosynchronous orbits are geostationary.

[R] A geostationary orbit stays exactly above the equator, whereas a geosynchronous orbit may swing north and south to cover more of the Earth's surface.

(a)    both the statements are correct and correct explanation

(b)    both the statements are correct and does not explanation the statement

(c)    [A] is correct but [R] is wrong

(d)   [A] is wrong but [R] is correct

3.      An elliptical orbit used to transfer between two circular orbits of different altitudes, in the same plane-

(a)    bi-elliptic transfer

(b)   Hohmann transfer

(c)    Low energy transfers

(d)   All of these

4.      What is/are the condition followed for Gravity-free Drag-free Space Flight

(a)    Far away from any massive body ⇒no gravity

(b)   Far away from any sensible atmosphere ⇒no aerodynamic forces

(c)    Only force applied is from rocket motor

(d)   All of the above

5.      Forces acting on a vehicle in the atmosphere will be

(a)    Gravity

(b)   Aerodynamic force

(c)    Thrust

(d)   All of the above

6.      Thrust – to – weight ratio for Large surface launched vehicles:

(a)   1.2-2.2

(b)   5.4-6.8

(c)    10-50

(d)   50-100

7.      Thrust – to – weight ratio for Small missiles:

(a)    1.2-2.2

(b)   5.4-6.8

(c)    10-50

(d)   50-100

8.      For a vehicle in gravitation-less space, to boost the vehicle velocity by 1500 m/sec, if the effective motor exhaust velocity is 2100 m/sec. If the initial total vehicle mass is 4400 kg, the corresponding propellant masses

(a)    220.3 kg

(b)   899.7 kg

(c)    2151.6 kg

(d)   2246.1 kg

9.      Compute the propellant mass required to a mission orbit requiring a velocity impulse of 4400 m/s. Assume that the burnout mass of the rocket structure is 2000 kg and that the specific impulse of the propellant (LO2/LH2) and rocket motor combination is 460 sec.

(a)    330.5 kg

(b)   530.5 kg

(c)    3305 kg

(d)   5305 kg

10.      For an elliptical orbit,

(a)     Perigee velocity is equal to apogee.

(b)   Perigee velocity is less than apogee.

(c)    Perigee velocity is greater than apogee.

(d)   perigee velocity does not affect apogee

11.      If 0°≤i<90°, the satellite orbits in the same direction as the earth’s rotation (orbit­ing eastward around the earth)

(a)    equatorial orbits

(b)   prograde orbit.

(c)    retrograde orbit

(d)   Polar orbits

12.      If 90°<i≤180°, the satellite orbits in the opposite direc­tion of the earth’s rotation (orbiting westward about the earth)

(a)    equatorial orbits

(b)   prograde orbit.

(c)    retrograde orbit

(d)   Polar orbits

13.      Consider an initial circular, LEO at a 200km.What velocity would be required to produce an elliptical orbit with a 200km altitude at periapsis and 2000km altitude at apoapsis?[R_E= 6400km]

(a)   0.45

(b)   0.54

(c)    0.62

(d)   0.77

14.      What will be the sign change when the velocity added to a spacecraft initial velocity changed from the initial to final orbit?

(a)    Zero

(b)   Positive

(c)    Negative

(d)   Positive or negative

15.      Considering a circular Mars orbit of radius 8000km to an apogee orbit radius 15000 km. The time for transfer is [Take:- ]

(a)    0.26 hr

(b)   1.04 hr

(c)    5.2 hr

(d)   10.4 hr

16.      A spacecraft launched from a circular orbit of radius 9100km to a final coplanar, elliptical orbit with eccentricity of 0.1 and perigee radius of 9000 km.[ .

A.    The flight path angle on the final orbit is-

(a)   2.508 deg

(b)   – 2.508 rad^-1

(c)    28.464 deg

(d)   331.536 rad^-1

B.     The velocity change necessary to convert from the initial to the final orbit(in km/s)

(a)    0.292

(b)   0.416

(c)    0.618

(d)   0.910

17.      Which of the following statement is correct for a Hohmann transfer between two circular coplanar orbits?

(a)    The apoapsis radius equal to radius of the initial orbits and the periapsis radius equal to radius of the final orbit.

(b)   The periapsis radius equal to radius of the initial orbits and the apoapsis radius equal to radius of the final orbit.

(c)    The periapsis radius less than radius of the initial orbits and the apoapsis radius equal to radius of the final orbit.

(d)   The apoapsis radius equal to radius of the initial orbits and the periapsis radius greater than radius of the final orbit.

18.      Pick the appropriate option , according to the corresponding propellant with an  increasing Specific Impulse

(a)    Nitric acid/mono-methyl-hydrazine < Cold Gas < Mono-propellant-hydrazine < LO2/LH2

(b)   Mono-propellant-hydrazine < Cold Gas < LO2/LH2 < Nitric acid/mono-methyl-hydrazine

(c)    Cold Gas < Mono-propellant-hydrazine < Nitric acid/mono-methyl-hydrazine < LO2/LH2

(d)   Mono-propellant-hydrazine < Cold Gas < Nitric acid/mono-methyl-hydrazine < LO2/LH2

19.      If the wedge half angle θ is greater than θ_max , the shock becomes

(a)    Oblique shock

(b)   Normal shock

(c)    Bow shock

(d)   Expansion shock

20.      An incompressible fluid flows over a flat plate with zero pressure gradients. The boundary layer thickness is 1mm at a location where Reynolds number is 1000.If the velocity of the fluid alone is increased by a factor of 4, then the boundary layer thickness at the same location , in mm will be

(a)    0.25

(b)   0.5

(c)    2

(d)   4

strength of material m.c.q

1) Find the modulus of elasticity for a rod, which tapers uniformly from 35mm to 15mm diameter .The rod is subjected to an axial load of 5KN.If the extension in the rod is 0.025 mm for a length of 300 mm rod
a)145.51GPa b)150 GPa c)155GPa d )160GPa

2) A bar uniform strength follows this condition. If “A”, “a” are areas of upper and lower ends of bar. “W” is the weight per unit volume, S=uniform stress in the bar, L=length of the bar
a) A=a exp(WL/S) b)A=a exp(WLS) c)A=a exp(W/LS) d)none

3) The strain due to temperature change in the bar? If a= coefficient of thermal expansion, t=temperature change
a) at b)a/t c)t/a d)a-t

4) If a material having young’s modulus 1.2*105 N/mm2 and bulk modulus of elasticity of 0.8*105 N/mm2 .Then poisons ratio is
a) 0.5 b) 0.25 c) 0.6 d)0.7

5) If a rigidly connected bar of steel and copper is cooled .then steel bar will be subjected to
a) tension b)compression c)shear d)none

6) Rate of change of bending moment with respect to length of beam is
a) shear force b)shear force per unit area c)zero d)infinite

7)The point where the sign of the bending moment is changing is called as
a)point of inflection b) point of contra flexure c)point of shear d)none

8)A steel plate of 60mm wide &120 mm thick is to be bent into a circular arc of radius 15 m,E=2*105 N/mm2.Then maximum bending stress will be?
a)800N/mm2 b)900N/mm2 c)1000N/mm2 d)none
9)A beam of length L is hinged at both ends ,is used as a column, What is effective length?
a)L b)2L c)L/2 d)3L

10) The ratio of average shear stress to maximum shear stress in case of rectangular beam is ?
a) 1.5 b) 0.66 c) 1 d) 2.

11)A freely supported beam is subjected to udl throughout the span ,the shape of BMD IS
a)rectangle b)equilateral triangle c)parabola d)none

12)Angle between principal planes is
a)360 deg b)90 deg c)45 deg d)0 deg

13)A solid round bar 3 m long&5 cm in diameter is used as strut with both ends hinged .Determine crippling load E=2*105 N/mm2
a) 67.3 KN b)70KN c)77KN d)80KN

14)The mohr’s circle reduces to point when body is subjected to
a)pure shear only
b)uni axial shear only
c)equal and opposite axial stress on two mutually perpendicular planes being free of shear\
d)equal axial stress on mutually perpendicular planes and planes being free of shear

15)A circular rod of 100 mm diameter &500 mm length is subjected to tensile force of 1000 KN. Determine the modulus of rigidity(G).? If E=2*105 N/mm2 and poisons ratio=0.3
a)0.3*105N/mm2 b)0.5*105 N/mm2 c)0.7*105N/mm2 d)0.2*105N/mm2

16)Two shafts A &B are made of same material. The diameter of shaft B is twice that of shaft A. The ratio of power which can be transmitted by shaft A to that of shaft B is
a)1/4 b)1/16 c)1/8 d)1/2

17)The shear stress distribution over a rectangular cross section of a beam follows
a)a straight line path b)an elliptical path c)a circular path d)a parabolic path

18)A shaft is initially subjected to a bending moment and then was subjected to torsion if magnitude of bending moment is found to be same as that of torque, then the ratio of maximum bending stress to shear stress would be
a)0.5 b)0.25 c)2 d)4

19) Thermal stress is function of
a)modulus of elasticity b)coefficient of linear expansion c)change in temperature 4)all of the above

20) The Euler load for column is 1000KN,and crushing load is 1800KN,the Rankine load is equal to
a)600KN b)1000KN c)1500KN d)2500KN

21)____theory which is applied to brittle materials

22)_____theory which is applied to ductile materials

23)formula for factor of safty is_____

24)formula for bulk modulus______

25)Elongation due to selfwight in the cylindrical bar is___of the elongation due to external load

26)Principal planes are the planes having the shear stress value equals to_____

27)The ratio between change in volume to original volume of a body is called as_____

28)unit of volumetric strain_____

29)At maximum bending moment ,shear force equals to____

30)The relationship between youngs modulus E,shear modulus G,when poisons ratio is zero_____

KEY
1)a
2)a
3)a
4)b
5)c
6)a
7)b
8)a
9)a
10)b
11)b
12)b
13)a
14)d
15)c
16)c
17)d
18)c
19)d
20)a
21)maximum normal stress criterion(columbs criterion)
22)maximum distortion energy criterion(von mises criterion)/maximum shearing stress criterion
23)yield point stress/working stress for ductile materials
Ultimate stress/working stress for brittle materials
24)direct stress/volumetric strain
25)0.5 times
26)zero
27)volumetric strain
28)No unit
29)zero
30)E=2G

CFD Analysis of Wind Turbine Blade With Winglets

ABSTRACT

This study is aimed at investigating the aerodynamic performance of the wind turbine blade with winglets and compares its performance in terms of the power generated with a regular straight blade without winglet. Adding a winglet to the wind turbine blade improves the power production without increasing the projected rotor area. A parameter study is carried out where two of the key parameters which describe a winglet design namely the cant angle and the winglet height are varied. The winglet is bent towards the pressure (upstream) side. Pro/ENGINEER is used to generate a straight wind turbine blade which is then modified in SPACECLAIM to attach a winglet to it. Single blade analysis approach is chosen to carry out the computation, as this involves less computational time and low cost. Results show that adding a winglet to a straight blade increases its power output by 2% to 20%. In addition, winglet which has a cant angle of 45° performs better, generating more power than the winglet which is perpendicular to the blade (cant angle 90°). Also, the power generation increases with the increase in the winglet height. Amongst the four winglet designs discussed, the design W4 with cant angle of 45° and winglet height of 4% rotor radius performs the best resulting in 20% improvement in the power generation when added to a straight blade.

Aerodynamics Quest M C Q

1. The amount of lift depends on these things:
a) the wing's airfoil shape  
b) angle of attack 
c) speed of flight
d) All of the above

2. The top surface of the wing has more camber than the bottom surface, the air flows faster over the top of the wing than it does underneath. The difference in air pressure above and below the wing causes
a) Lift
b) Drag
c) Thrust
d) both lift and Thrust

3.Long slender wings like those on a sail-plane are 
a) low AR
b) medium AR
c) high AR
d) AR unpredictable.

4. High speed air-planes ,like modern jet fighters have - 
a) no sweep
b) lower sweep
c) greater sweep
d) either b) or c)

5. Air density is measured by how tightly compressed the molecules are. When there are more molecules in the air (greater density), 
a) it is easier to generate lift
b) it is more difficult to generate lift
c) unpredictable
d) no lift will produce

6. The amount of drag depends on -
a) size of the aircraft 
b) details of the shape and smoothness of the aircraft 
c) lifting efficiency of the wing 
d) All of the above

XFOIL vs CFD performance predictions for high lift low Reynolds number airfoils

Abstract

Blade Element Momentum (BEM) theory is an extensively used technique for calculation of propeller aerodynamic performance. With this method, the airfoil data needs to be as accurate as possible. At the same time, Computational Fluid Dynamics (CFD) is becoming increasingly popular in the design and optimization of devices that depend on aerodynamics. For fixed and rotary wing applications, the airfoil lift over drag coefficient is the dominant airfoil performance parameter. Selecting a suitable computational tool is crucial for the successful design and optimization of this ratio. The XFOIL code, the Shear Stress Transport k−ω$$ turbulence model and a refurbished version of k−kl−ω$$transition model were used to predict the airfoil aerodynamic performance at low Reynolds numbers (around 2.0×10⁵$\mathrm{}{\mathrm{}}^{\mathrm{}}$). It has been shown that the XFOIL code gives the overall best prediction results. Also, it is not clear that CFD turbulence models, even with boundary layer transition detection capability, can compute better airfoil performance predictions data.

Keywords

• XFOIL; 
• Airfoil analysis; 
• k−kl−ω$$ modified transition model; 
• k−ω$$ SST turbulence model