Consider a thin,
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Fundamentals of Heat and Mass Transfer
- We are testing a flat plate of length L = 1.125 m and width W = 0.225 m in a stream of air flowing with a velocity of 20 m/s. In test case 1, the air is flowing parallel to L and in test case 2 air is flowing parallel to W. Find: What portion of the boundary layer flow is laminar in each case? What is the highest laminar boundary layer thickness in each case? Assuming the flow is entirely turbulent over the plate, calculate the drag force in both test cases Take air density as 1.2 kg/m3 and its viscosity as μ=18×10−6μ=18×10−6 N.s/m2.arrow_forwardConsider the same Lockheed F-104 supersonic fighter shown, with the same flight conditions of Mach 2 at an altitude of 11 km. For these conditions the wing angle of attack is α = 0.035 rad = 1.98◦. Assume the chord length of the airfoil is 2.2 m, which is approximately the mean chord length for the wing. Also, assume fully turbulent flow over the airfoil. Calculate: (a) the airfoil skin friction drag coefficient, and (b) the airfoil wave-drag coefficient. Compare the two values of drag.arrow_forwardThe wing of the Fairchild Republic A-10A twin-jet close-support airplane is approximately rectangular with a wingspan (the length perpendicular to the flow direction) of 17.5 m and a chord (the length parallel to the flow direction) of 3 m. The airplane is flying at standard sea level with a velocity of 200 m/s. Assume the wing is approximated by a flat plate and incompressible flow. If the critical Reynolds number for transition is 106, calculate the skin friction drag for the wing. Use turbulent drag as 2830 N. (Round the final answer to the nearest whole number.)arrow_forward
- 2.A fluid at a temperature of 75 oC flows at a speed of 10 m/s across a pipeouter diameter of 5 cm.Calculate the drag coefficient and drag force per meter length if the fluid flowing is:a) Air at a pressure of 1 atmb) CO2 gas at a pressure of 1 atm liquidd) Ethylene glycole) Engine oilf) What is your discussion and conclusion?arrow_forwardThe forming section of a plastics plant puts out a continuous sheet of plastic that is 1.2 m wide and 2 mm thick at a rate of 18 m/min. The sheet is subjected to airflow at a velocity of 4 m/s on both top and bottom surfaces normal to the direction of motion of the sheet. The width of the air cooling section is such that a fixed point on the plastic sheet passes through that section in 2 s. Using properties of air at 1 atm and 60°C, determine the drag force the air exerts on the plastic sheet in the direction of airflow.arrow_forwardThere are numerous occasions in which a fairly uniform free-stream flow encounters a long circular cylinder aligned normal to the flow. Examples include air flowing around a car antenna, wind blowing against a flag pole or telephone pole, wind hitting electrical wires, and ocean currents impinging on the submerged round beams that support oil platforms. In all these cases, the flow at the rear of the cylinder is separated and unsteady, and usually turbulent. However, the flow in the front half of the cylinder is much more steady and predictable. In fact, except for a very thin boundary layer near the cylinder surface, the flow field may be approximated by the following steady, two-dimensional velocity components in the xy- or r?-plane:arrow_forward
- Experimental measurements of the convection heat transfer coefficient for a square bar in cross flow yielded the following values: Assume that the functional form of the Nusselt number is Nu = C*Rem*Prn, where C, m, and n are constants. Also, assume that air temperature does not change in the following problem.A. What will be the convection heat transfer coefficient for a similar bar with L = 1 m when V = 15 m/s?B. What will be the convection heat transfer coefficient for a similar bar with L = 1 m when V = 30 m/s?arrow_forwardExplain briefly in your own words (parts a-d)a) Why doesn’t the surface roughness affect the pressure drop in a laminar pipe flow? b) For bluff bodies, the drag coefficient decreases abruptly when the flow becomes turbulent. Why? c) Consider a spinning ball (in the clockwise direction) moving with a velocity U. Explain how the lift force is formed on the ball and show its direction. Uwd) For flow over streamlined bodies, drag force usually increases when the flow becomes turbulent.Why? e) Consider a pipe with a radius R and length L (extending from (1) to (2)). Inside the pipe there is a solid cylinder with a radius k×R (k 1). The planes (1) and (2), separated by a distance L have pressures P1 and P2 respectively, with P1 > P2. At t = 0, the inner solid cylinder suddenly begins to be pulled at a constant speed U in the negative z direction. Thefluid is an incompressible Newtonian liquid with dynamic viscosity μ and density ρ. In orderto find the solution for the velocity field in…arrow_forward1. The flow over a leaf is being studied in a wind tunnel. If the wind blows at 8 mph, and the leaf is aligned with the flow, is the boundary layer laminar or turbulent? 2. For steady, fully developed flow of a constant property fluid in a two-dimensional, rectangular duct of height 2h the velocity profile is parabolic. Find the ratio of the displacement thickness δ∗ to the half-height h (assume you can put the freestream velocity equal to the maximum velocity, and h equal to the boundary layer thickness).arrow_forward
- For each case, calculate an appropriate Reynolds number and indicate whether the flow can be approximated by the creeping flow equations. (a) A microorganism of diameter 5.0 μm swims in room temperature water at a speed of 0.75 mm/s. (b) Engine oil at 140°C flows in the small gap of a lubricated automobile bearing. The gap is 0.0016 mm thick, and the characteristic velocity is 15 m/s. (c) A fog droplet of diameter 10 μm falls through 30°C air at a speed of 4.0 mm/s.arrow_forwardA hemispherical gasoline droplet is formed on the fuel pump nozzle outlet. Estimate the maximum diameter before it falls off. Assuming following properties: p = 750 g/L.arrow_forwardA particle of 2 mm in diameter and density of 2500 kg/m3 issettling in a stagnant fluid in the Stokes’ flow regime.a) Calculate the viscosity of the fluid if the fluid density is 1000kg/m3 and the particle falls at a terminal velocity of 4 mm/s.b) What is the drag force on the particle at these conditions?c) What is the particle drag coefficient at these conditions?d) What is the particle acceleration at these conditions?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning