In 1934, Woelfle developed a shield similar to the Nipher based on wind tunnel tests.
The Woelfle windbreak ring is equipped with vertically arranged metal blades in a circle. The metal blades are fixed and conically converge at the base of the rain gauge. The individual blades are connected by a ring.
The wind protection ring according to Woelfle consists of:
· Standpipe for the rain gauge
· frame
· Metal slats
· Small parts for assembly
1. Measuring height
The wind shield according to Tretjakov is used for the measuring height 100 cm offered.
The existing foundations and threaded pins on the measuring field are used for installation.
The windshield is made of V2A 1475. A service life of 10 years is guaranteed for use under average meteorological conditions. This guarantee cannot be given for use on islands.
2. Structure
2.1. The Ring
The Woelfle windbreak consists of 21.35 cm long, circularly arranged metal slats. The metal strips are trapezoidal and U-shaped.
The arrangement on the circle with a diameter of 1060 mm is carried out at the same distance using slots.
This also ensures that the metal slats can be easily replaced.
The slats are arranged vertically in a fixed position. This prevents them from becoming blocked at high flow velocities, depending on the flow direction and wind speed.
3. Modifications
The aerodynamic shape of the upper ends of the metal slats is at an angle of almost 90°.
4. Maintenance
To facilitate maintenance of the rain gauge, one element of the ring is designed to be hinged. The element is attached with wing screws and can be removed without tools.
5. The frame
The supports are at a 120° angle They are mounted offset and taper towards the foundation base. The supports are secured using the pins provided on the foundation.
The supports and all connecting components are made of V2A stainless steel. The entire structure is also height-adjustable at the supports. This allows the system to be re-levelled and adapted to the requirements of the measuring point.
6. Miscellaneous
The windshield can be retrofitted with a holder for an anemometer to correct the precipitation values.
