Study of the Head Loss Associated with a Fluid Flowing through a - PowerPoint PPT Presentation

Study of the Head Loss Associated with a Fluid Flowing through a Porous Screen Channing R.C. Santiago, REU Student Ted Chu, Graduate Mentor and K. H. Wang, Faculty Mentor Department of Civil and Environmental Engineering University of Houston Houston, Texas

Common Applications of Screens • Fish Screens • Removal of Debris • Capture Solid Waste All these screens have a common goal in terms of head loss.

Possible Applications • Wave Energy Dissipation  Coastal Structures  Ship Channels

THEORETICAL BACKGROUND

Head Loss (ΔH) Screen Flow • energy loss Y 1 Y 2 θ Energy Equation

Porosity (ø) • The ratio of the open area of the screen to the total area. Round – 60º Staggered Center

Normal Velocity Continuity Equation Screen V 1 S L Y 1 Other Identities: V n 1) θ 2)

Darcy’s Law L Q b a A • Describes a flow through a porous medium • k: Intrinsic Permeability • ν(nu): Kinematic Viscosity

Equation Proposed by Forchheimer • Darcy’s law is not valid for all flows through porous media Darcy flow Non-Darcy flow

Reynolds Number • Used to locate the point at which the flow switches from Darcy to non-Darcy

Experiments

The Hydraulic Lab

Screens 1/4” Diameter Holes 1/8” Diameter Holes Ø = 0.4031

Screens 3/32” Diameter Holes 1/16” Diameter Holes Ø = 0.2267

Screen Brace

Profile of Flow Through Screen 90º 75º 68º 59º

Flow Rates (Q) 1/4” and 1/8” screens (ø = 0.4031) • 0.10, 0.20-2.20 (cfs) 3/32” and 1/16” screens (ø = 0.2267) • 0.10, 0.20-1.60 (cfs)

Results

General Trend • Decreasing flow rate = decrease in ΔH • Decreasing angle of inclination = decrease in ΔH

Formulating an Equation (ΔH is proportional to V^2/2g ?)

Formulating an Equation • Next, we plot ΔH vs. V^2/2g Angle of inclination is not considered.

Formulating an Equation Plot of ΔH vs. (V 1 sinθ)^2/2g A transition in the plot.

Formulating an Equation

Formulating an Equation: ø = 0.4031 1 st Half  Function is x 1/2  Forchheimer’s Equation Darcy flow

Formulating an Equation: ø = 0.4031 2 nd Half • Function is linear • Forchheimer’s Equation Non-Darcy flow

Formulating an Equation: ø = 0.2267 • Function is linear 1 st Half Darcy flow

Formulating an Equation: ø = 0.2267 2 nd Half ???

Critical Reynolds Number Ø = 0.4031 Ø = 0.2267

Conclusions • General Trend • Porosity is More of a Factor than Pore Size • No Apparent Trend with Critical Reynolds Number • More Testing is Needed