Wind Tunnel Calibration.docx

Wind Tunnel Calibration

Name: Animesh Phatowali Roll no: 17AE30005 Group: 6 Experiment :7

Date of experiment: 15/3/19 Date of submission: 22/3/19

Aim: To measure the velocity profile across the wind tunnel using a pitot tube and manometer.

Apparatus: 1. Low speed wind tunnel 2. Manometer 3. Pitot tube

Theory: Wind tunnels are large tubes through which air is pass through and the behaviour of the air is notes when air is passes through various specimens. Low speed wind tunnels have speed of air which have very low Mach (M<0.4). In this experiment we are using open wind tunnel in which two principles are used 1. Continuity equation 2. Bernoulli’s equation We use the continuity equation to increase the velocity of air in the test section and to calculate the velocity inside the test section we use Bernoulli’s equation.

Observations:

Group 1/2: 𝑝𝑟 = 260, POSITION

𝑃𝑠𝑡𝑎𝑡𝑖𝑐

𝑝∞ = 244 𝑃𝑡𝑜𝑡𝑎𝑙

V1

240

256

V2

240

258

V3

244

260

V4

242

258

V5

240

258

H1

240

258

H2

240

256

H3

244

260

H4

240

258

H5

240

258

Group 3/4: 𝑃𝑟 = 254, Position

𝑃𝑠𝑡𝑎𝑡𝑖𝑐

𝑃∞ = 234 𝑃𝑡𝑜𝑡𝑎𝑙

V1

232

254

V2

228

254

V3

226

254

V4

226

254

V5

226

254

H1

228

252

H2

226

250

V3

226

254

H4

226

250

H5

226

250

Group 5/6: 𝑃𝑟 = 258,

Position

𝑃𝑠𝑡𝑎𝑡𝑖𝑐

𝑃∞ = 242

𝑃𝑡𝑜𝑡𝑎𝑙

V1

235

255

V2

236

256

V3

236

256

V4

235

256

V5

235

255

H1

236

255

H2

236

254

V3

236

256

H4

235

255

H5

236

256

Group 7/8: 𝑃𝑟 = 252,

Position

𝑃𝑠𝑡𝑎𝑡𝑖𝑐

𝑃∞ = 228

𝑃𝑡𝑜𝑡𝑎𝑙

V1

220

248

V2

220

248

V3

220

250

V4

220

248

V5

220

248

H1

224

250

H2

220

250

H3

220

250

H4

220

250

H5

220

248

Group 1/2:

Group 3/4:

Group 5/6:

Group 7/8:

Discussion: 1. Based on flow speed calculate the Mach number Ans. 𝑀𝑎𝑐ℎ =

𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑎𝑖𝑟 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑠𝑜𝑢𝑛𝑑

=

18.31 330

= 0.05

2. What is the use of honeycomb section of wind tunnel? Ans. honeycomb, is a device used to straighten the air flow in a wind tunnel. It is a passage of ducts, laid along the axis of main air stream to minimize the lateral velocity components caused by swirling motion in the air flow during entry. 3. Is the flow uniform in your experiment? What causes the nonuniformity? Ans. The error in the experiment is within the tolerance limit. So the flow in the experiment is uniform. There is some non-uniformity in the experiment due to human errors, swirl turbulence etc.

Conclusion: In the experiment we found that the variation in the velocity of air is small in the air and so the flow is uniform and thus the wind tunnel is calibrated.