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 HM 170.28 Wake Measurement
 Technical Description

Boundary layer flows form when flowing around drag bodies. In the wake of the body under surrounding flow, these boundary layer flows meet each other and form turbulence that leads to the velocity in this region being reduced. The reduction in velocity leads to a decrease in the dynamic pressure
The HM 170.28 experimental unit - used in the wind tunnel HM 170 - allows the wake on a cylinder surrounded by flow to be measured. To record the total pressures, the experimental unit contains a wake rake consisting of 15 Pitot tubes. Each Pitot tube is fitted with a hose connection. The wake rake can be mounted at two different distances from the cylinder.
The total pressures are displayed on the tube manometer HM 170.50 or in the electronic pressure measurement HM 170.55. The pressure curve shown there clearly indicates the so-called wake depression. As a key parameter, the drag coefficient of the body flowed around can be determined from the pressures. In addition, the drag coefficient can be determined by measuring the drag force.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- detect pressure distribution using wake rake
- demonstrate wake depression
- determine drag coefficient by pressure distribution

in the wake of the cylinder
- determine Reynolds number
- measurement of drag with the two-component force

sensor from HM 170
- determine the drag coefficient via the drag force
- comparison of the two methods for determining the

drag coefficient

 Features

* Investigation of the wake when flowing around

the cylinder1
* Wake rake with 15 Pitot tubes1
* Determine the drag coefficient for cylinders

 Available accessories
HM 170.50 -- 16-Tube Manometer, 600mm
HM 170.55 -- Electronic Pressure Measurement, 18x 0...500Pa
 Specification [1] investigation of the wake when flowing around a cylinder[2] accessories for HM 170 Open Wind Tunnel[3] cylinder as drag body[4] wake rake with 15 Pitot tubes detects total pressures [5] measurement of drag via two-component force sensor from HM 170[6] removable spacer plate allows two wake rake positions for measurement[7] display of the pressures on the 16-tube manometer HM 170.50 or in the electronic pressure measurement HM 170.55 Technical Data Cylinder- d=20mm- height: 100mm- height with supporting rod: 290mmWake rake- 15 Pitot tubes- inner diameter: 1,1mm- outer diameter: 2mm- distance between the Pitot tubes: 3mm Dimensions and Weight LxWxH: 237x52x175mmWeight: approx. 3kg Required for Operation Scope of Delivery 1 experimental unit1 wake rake1 cylinder1 measuring hose1 set of instructional material Order Details 070.17028  HM 170.28  Wake Measurement