Wind Tunnel Modeling of Echo and Climbing Dunes

This chapter describes the wind tunnel modeling of echo and climbing dunes. Eolian sand dunes originate as accretions of sand on existing sand patches, and may develop independent of fixed surface features. It is found that apart from these self-accumulated dunes, sand accumulations are found in front of, or behind, topographic obstacles such as cliffs, shrubs, and boulders. The data concerning the formation of echo and climbing dunes gathered during wind tunnel tests made on several simulated cliffs with different inclinations is presented in the chapter. Three types of measurements were taken, including the modeling of echo and climbing dunes in front of simulated cliffs, tracing of eddies and wind turbulence in front of the simulated cliffs and over echo dune models and through a bubble generator, and measurements of wind velocity (with a hot-wire anemometer) in front of the simulated cliffs and over the echo dune models. It is observed that when echo dune models built of wood were placed in front of the simulated cliff with shape and position similar to those modeled with sand the bubbles showed constant and prominent reverse-flow eddies between the dune and the cliff.