RND_EDGE_GRILL
Computes the pressure-loss coefficient K for a rounded square grill, square bar screen, or perforated plate with rounded edges from the open-area fraction \alpha.
The base correlation uses an empirical lookup in \alpha. When thickness l, hydraulic diameter D_h, and Darcy friction factor f_d are all supplied, the source adds a friction term to the lookup value:
K = K_{\text{lookup}} + \frac{f_d l}{\alpha^2 D_h}
The documented correlation applies for 0.3 \leq \alpha \leq 0.7, and the reported loss coefficient is referenced to the upstream approach velocity.
Excel Usage
=RND_EDGE_GRILL(alpha, l, Dh, fd)alpha(float, required): Fraction of grill open to flow (must be 0.3-0.7), [-]l(float, optional, default: null): Thickness of the grill or plate, [m]Dh(float, optional, default: null): Hydraulic diameter of gap in grill, [m]fd(float, optional, default: null): Darcy friction factor, [-]
Returns (float): Loss coefficient K, [-], or error message (str) if input is invalid.
Example 1: Rounded-edge grill at alpha 0.4 without friction correction
Inputs:
| alpha |
|---|
| 0.4 |
Excel formula:
=RND_EDGE_GRILL(0.4)Expected output:
1
Example 2: Rounded-edge grill with friction correction inputs
Inputs:
| alpha | l | Dh | fd |
|---|---|---|---|
| 0.4 | 0.15 | 0.002 | 0.0185 |
Excel formula:
=RND_EDGE_GRILL(0.4, 0.15, 0.002, 0.0185)Expected output:
9.67187
Example 3: Rounded-edge grill at mid-range openness alpha 0.5
Inputs:
| alpha |
|---|
| 0.5 |
Excel formula:
=RND_EDGE_GRILL(0.5)Expected output:
0.6
Example 4: Rounded-edge grill at the upper valid alpha bound
Inputs:
| alpha |
|---|
| 0.7 |
Excel formula:
=RND_EDGE_GRILL(0.7)Expected output:
0.2
Python Code
Show Code
from fluids.filters import round_edge_grill as fluids_round_edge_grill
def rnd_edge_grill(alpha, l=None, Dh=None, fd=None):
"""
Calculate the loss coefficient for a rounded edge grill or perforated plate.
See: https://fluids.readthedocs.io/fluids.filters.html#fluids.filters.round_edge_grill
This example function is provided as-is without any representation of accuracy.
Args:
alpha (float): Fraction of grill open to flow (must be 0.3-0.7), [-]
l (float, optional): Thickness of the grill or plate, [m] Default is None.
Dh (float, optional): Hydraulic diameter of gap in grill, [m] Default is None.
fd (float, optional): Darcy friction factor, [-] Default is None.
Returns:
float: Loss coefficient K, [-], or error message (str) if input is invalid.
"""
try:
# Validate and convert alpha
try:
alpha = float(alpha)
except (ValueError, TypeError):
return "Error: alpha must be a number."
# Validate alpha range (0.3 to 0.7 for round_edge_grill)
if alpha < 0.3 or alpha > 0.7:
return "Error: alpha must be between 0.3 and 0.7."
# Validate and convert optional parameters
if l is not None:
try:
l = float(l)
except (ValueError, TypeError):
return "Error: l must be a number."
if l <= 0:
return "Error: l must be positive."
if Dh is not None:
try:
Dh = float(Dh)
except (ValueError, TypeError):
return "Error: Dh must be a number."
if Dh <= 0:
return "Error: Dh must be positive."
if fd is not None:
try:
fd = float(fd)
except (ValueError, TypeError):
return "Error: fd must be a number."
if fd <= 0:
return "Error: fd must be positive."
result = fluids_round_edge_grill(alpha=alpha, l=l, Dh=Dh, fd=fd)
if result != result or result in (float('inf'), float('-inf')):
return "Error: Result is not finite."
return float(result)
except Exception as e:
return f"Error: {str(e)}"