Turbulence in Waving Wheat

Measurements of mean and fluctuating velocities, surface pressure and stalk waving have been made in a uniform wheat canopy. Features of the vertical profiles of mean turbulence quantities are discussed in the context of the resonant waving of wheat stalks. The discrete and prominent peaks in the velocity spectra measured in and above the canopy are then analyzed in the light of the organized travelling wave-type structure or ‘honami’, observed in such crops on windy days. Prominent peaks in the spectra are identified with the arrival of gusts, the stalk-waving frequency, and the frequency of oscillations in canopy height. Two possible mechanisms are proposed to account for the observed height dependence of the peak frequencies, directly associated with stalk waving.

[1]  A. Weiss,et al.  The flux‐angle distribution of momentum as determined from propeller anemometer measurements , 1976 .

[2]  E. Mollo-Christensen.  Intermittency in Large-Scale Turbulent Flows , 1973 .

[3]  Ronald M. Cionco,et al.  Intensity of turbulence within canopies with simple and complex roughness elements , 1972 .

[4]  John L. Lumley,et al.  The structure of atmospheric turbulence , 1964 .

[5]  P. Mulhearn.  On the structure of pressure fluctuations in turbulent shear flow , 1975, Journal of Fluid Mechanics.

[6]  J. Hunt,et al.  Turbulent wind flow over a low hill , 1975 .

[7]  E. Mollo-Christensen,et al.  Observation of the Structure on Moving Gust Patterns Over a Water Surface (“Cat's Paws”) , 1973 .

[8]  Iehisa Nezu,et al.  Prediction of the contributions to the Reynolds stress from bursting events in open-channel flows , 1977, Journal of Fluid Mechanics.

[9]  R. Shaw.  Secondary Wind Speed Maxima Inside Plant Canopies , 1977 .

[10]  L. H. Allen,et al.  Turbulence and Wind Speed Spectra within a Japanese Larch Plantation , 1968 .

[11]  P. Davies.  Structure of turbulence , 1973 .

[12]  C. Sleicher,et al.  Turbulence measurements with inclined hot-wires Part 2. Hot-wire response equations , 1967, Journal of Fluid Mechanics.

[13]  P. Mulhearn,et al.  A simple mathematical model of airflow in waving plant canopies , 1978 .

[14]  J. Finnigan,et al.  Modelling waving crops in a wind tunnel , 1978 .

[15]  W. Willmarth,et al.  Measurements of the structure of the Reynolds stress in a turbulent boundary layer , 1973, Journal of Fluid Mechanics.

[16]  K. Inoue,et al.  Studies of Energy and Gas Exchange within Crop Canopies (10) Structure of turbulence in rice crop , 1975 .

[17]  Rene Chevray,et al.  Cross-wire anemometry in high intensity turbulence , 1975, Journal of Fluid Mechanics.

[18]  F. Champagne.  Turbulence measurements with inclined hot-wires , 1965 .

[19]  A. Grass.  Structural features of turbulent flow over smooth and rough boundaries , 1971, Journal of Fluid Mechanics.

[20]  E. F. Bradley,et al.  Turbulent flow in a model plant canopy , 1976 .

[21]  William K. Blake,et al.  Turbulent boundary-layer wall-pressure fluctuations on smooth and rough walls , 1970, Journal of Fluid Mechanics.

[22]  N. Wilson,et al.  A Higher Order Closure Model for Canopy Flow , 1977 .

[23]  J. Finnigan.  Turbulence in Waving Wheat , 1979 .

[24]  A. Hussain,et al.  The mechanics of an organized wave in turbulent shear flow. Part 3. Theoretical models and comparisons with experiments , 1972, Journal of Fluid Mechanics.

[25]  W. Willmarth,et al.  Structure of Turbulence in Boundary Layers , 1975 .