poster - International Conference of Agricultural Engineering

model was introduced to estimate the air flow turbulence. Using the wind velocity predicted
by this model, the vapor pressure and air temperature in the vicinity of the soil surface were
estimated by the numerical model describing the air heat and vapor transfer in the microadvective
condition. The energy budget on the soil surface was estimated using the wind
velocity, vapor pressure, and air temperature simulated by these models. The soil water
content and temperature were predicted using the simulation model describing the water and
heat transfer in the soil. Using the energy budget, the accuracy of this model was verified by
a wind tunnel.
2. Methodology
2.1. Analysis of airflow field around an isolated crop
The governing equations describing the wind flow around an isolated crop can be written as
follows:
∂u
∂v
+ = 0
∂x
∂z
∂u
∂u
∂u
1 ∂p
∂ ⎛
+ u + v = − + ⎜ K
∂t
∂x
∂z
ρ ∂x
∂x
⎝
∂v
∂v
∂v
1 ∂p
∂ ⎛
+ u + v = − + ⎜ K
∂t
∂x
∂z
ρ ∂z
∂x
⎝
a
a
∂u
⎞ ∂ ⎛
⎟ + ⎜ K
∂x
⎠ ∂z
⎝
∂v
⎞ ∂ ⎛
⎟ + ⎜ K
∂x
⎠ ∂z
⎝
a
a
∂u
⎞
⎟ − C
∂z
⎠
∂v
⎞
⎟ − C
∂z
⎠
where u and v are the wind velocity in horizontal and vertical directions (m·s -1 ), ρ is the air
density (=1.293kg/m 3 ), p is the air pressure (g·m -1·s -2 ), K a is the eddy diffusion coefficient
(m 2·s -1 ), C m is the resistance coefficient by crop canopy, S is the leaf area density(m 2·m -3 ) , t
is the time, x is the fetch, and z is the height.
Eddy coefficient described in eqs. (2) and (3) can be estimated as follows:
K
a
2 ∂u
= λ
m
(4)
∂z
The parameter λ m , inside and outside of the crop canopy can be represented as the following
equations, respectively.
3
2κ
λ
m in
= (5)
C m
S
( z − )
λ = κ
(6)
m out
d 0
The parameter of inside of the crop canopy λ m in can be estimated as follows:
( z − d ) 0 m in : = κ ( z − )
κ > λ
m in
d 0
m
m
S
S
u
u
2
2
+ v
+ v
λ (7)
2
2
v
u
(1)
(2)
(3)
κ z > λ
m
in
: λ = κz
(8)
m in
2.2. Heat and vapor transfer under micro-scale advection
The equations that describe the air heat and vapor transfer in the advective condition can be
written as follows: