Aquatic plants are open flexible structures - A reply to Sukhodolov

Abstract

1. Aquatic plant stands are flexible, mesh-like open structures that undergo modification in shape and experience a cascade of declining flow velocities and micro-scale Reynolds numbers with increasing distance into the stands. It is not possible to define or measure the frontal area of this open flexible plant structure. Total wetted area was used as a reference area for drag because it can be measured with high accuracy and it was the most suitable measure of plant size impeding the flow and absorbing light for photosynthetic production. What is important is that it is made absolutely clear which type of reference area that is used. 2. Numerous important relationships in biology are open to discussion because of differences in dimensions between variables. Relating dimensionless drag coefficients to dimensionless Reynolds numbers resolve such discussions, but defining Reynolds numbers cause other problems. Relating drag coefficients to macro-scale Reynolds numbers would result in exactly the same form of relationship as to water velocity because macro-scale Reynolds numbers changed in direct proportion to water velocity in the experiments, while kinematic viscosity and characteristic length within species remained constant.