Unsteady Flow in Pipes

Prof Tiit Koppel Department of Mechanics Tallinn University of Technology University of Brighton October 14, 2008

Unsteady Flow

n  Unsteady Flow n  Waterhammer

n  Steady Oscillatory Flow n  Periodic Flow (Pulsatile) n  Resonance

Hydraulic System

Shear Stress Probe

LDV

Pipe Section

Pipe Section

Start-up Flow

Turbulence Generation

Constant Pressure Gradient

2Rtν

τ =

αlg380.080.1lg * +=HU

zPRa∂

∂−= 2

3

νρ

Development of the Thickness of the Boundary Layer

Regions of Laminar and Turbulent Flows

Spectral Distribution

Turbulence Generation

Velocity Distribution

Acceleration from One Steady to Another

PIV Measurements

Calculated and Measured Pressure

Calculated Pressure

Set-up for Pulsating Flow with Heat Load

Temperature

20.2

20.4

20.6

20.8

21

21.2

21.4

21.6

21.8

22

22.2

0 1 2 3 4 5 6

Time(s)

Temperature(C*)

-

0.20000

0.40000

0.60000

0.80000

1.00000

1.20000

1.40000

1.60000

1.80000

Voltage(V)

IRCamera Flow Temp1 Temp2

Mean Temperature

Wall Temperature

Transient vaporous and gaseous cavitation in pipelines

TUT team: Janek Laanearu, Tiit Koppel and Ivar Annus

PROJECT FOCUS on cavitation processes in the fully- and partly-filled pipelines. Two-phase flow experiments are proposed in the DELTARES large-scale test facility made of PVC (D250) pipelines.

(EU HYDRALAB III PROJECT: Deltares dynamic multi-phase flow rig)

PVC test section (length 300 m)

1

3 4

5 6

by-pass 1. head tank (height 25 m)

2. high-pressure air tank (10 bar)

3 - 4. vertical pipes

5. upstream control valve

6. downstream control valve

flow to basement reservoir

2

Side view of Deltares test rig

Expected benefits from the use of the large installation

n  Better understanding of physics of large-scale flow in two-phase system

n  Validation of existing numerical codes and improvement of models

n  Economic design of new piping systems (water supply, hydropower, fluid transport)

n  Fast filling and emptying procedures for (fuel) transport and fire fighting systems

n  Safer operation of aging pipelines

Cavitation is a complex phenomenon that may appear in hydraulic machinery and pipe systems in several forms, affecting their operation in many different ways. Cavitation in hydraulic machinery may lead to reduction of the performance of pumps (head), turbines (efficiency) and valves (flow capacity), and produce erosion, vibrations and noise emission.

Water Hammer

Continuity 0sin

2=

∂∂

+Θ−∂∂

+∂∂

xV

gaV

xHV

tH

Momentum 02

=+∂∂

+∂∂

+∂∂

DVfV

xVV

tV

xHg

Two-phase Flow

0=

∂∂

−∂∂

+∂∂

xV

xV

tmv

mv αα

02

sin =+Θ+∂∂

+∂∂

DVfV

gxVV

tV mmm

mm

Discrete Cavitation

H

u0

c

T M V

p0

H uf

x

L = 300m

D = 250mm

Filling of the pipeline

p0

H uf

x

pa

D = 250mm

L = 300m

Drainage of the pipeline

Animation of the Water Hammer

n  Oil pipeline n  L = 10 km n  D = 900 mm n  C = 1100 m/s

Thank You for Your Attention!