Wake Measurement HM 170.28

Wake Measurement

Type: HM 170.28
Name: Wake Measurement

Boundary layer flows form when drag bodies are immersed in a flow. In the wake of the body immersed in a 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 immersed in a 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 manometers 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 in a flow can be determined from the pressures. In addition, the drag coefficient can be determined by measuring the drag force.

Technical details
  • investigation of the wake of a cylinder immersed in a flow
  • accessory for the wind tunnel HM 170
  • cylinder as drag body
  • wake rake with 15 Pitot tubes detects total pressures
  • measurement of drag via force sensor from HM 170
  • removable spacer plate allows two wake rake positions for measurement
  • display of the pressures on the 16 tube manometers HM 170.50 or in the electronic pressure measurement HM 170.55
  • Technical data


    • inner Ø: 20mm
    • height: 100mm
    • height with supporting rod: 290mm

    Wake rake

    • 15 Pitot tubes
    • inner Ø: 1,1mm
    • outer Ø: 2mm
    • distance between the Pitot tubes: 3mm
    Dimensions and weight

    LxWxH: 237x52x175mm
    Weight: approx. 3kg