violent in-chamber water column movement in an oscillating ... · in-chamber water behaviour :...

Conclusions: • The WC is more likely to slosh during higher wave height and less air resistance • The irregular wave condition is more likely to have a sloshing compares to regular wave condition with the (significant) same wave height. • Some amount of “sloshing” is not an uncommon situation and should be considered in design and performance assessment of an OWC chamber. Acknowledgement: Indonesian Endowment Fund for Education (LPDP) for first author Ph.D study The “GWK OWCs” project was an EC Hydralab III access project led by University of Edinburgh in collaboration with HR Wallingford, Second University of Naples, Queen’s University of Belfast, and the University of East Anglia Krisna Pawitan , William Allsop, Tom Bruce [email protected] 1. Sea water trapped in a chamber with the bottom still connected to the sea 2. As the wave rises and falls, the water column inside the chamber oscillates up and down 3. This movement drives the air in and out of the chamber via power take-off mechanism In-chamber water behaviour : Oscillating water column is one of the most studied wave energy converters (WECs) which utilised the wave’s up and down movement to generate electricity. The device excel among other WECs due to its simplicity and ability to be combined with a conventional breakwater, thus splitting the cost between energy generation and coastal defense. The water column inside the chamber is often assumed to be well-behaved during operation in the design stage. A series of physical model experiments, however, proved that such condition is not always the case. It was found that in-chamber water movement (sloshing and slams) appears under certain wave condition. This study aims to characterise the type of sloshing occurs and then identify the sea conditions under which the in-chamber water motion is more likely to occur. Description: • Bc/L : characteristics width • H/H m0 : (significant) wave height • Ao/Ac : opening:chamber area ratio Symbols: • / : no video available • ! : ceiling impact observed • ^ : water level reached the ceiling Closed 0.05 (0.06%) 0.1 (0.22%) 0.2 (0.88%) 0.3 (1.99%) 0.1 / / 0.15 / / / / 0.2 / / / 0.26 0.39 / / / / 0.52 0.65 / / / 0.78 ! 0.1 / / / 0.15 / / / / 0.2 / / 0.4 0.6 / / / 0.8 ! ! 1 / / / ! / 1.2 / / / / ! 0.54 ! ! 0.81 / ! / 1.07 / / / ! ! 1.61 / / / / ! 0.1 / / / 0.15 / / / / 0.2 / / / 0.34 0.67 ^ 1 / / / ! / 1.33 / / / / ! 0.0697 H (m) Bc/L Orifice Diameter in m (A o /A c ) 0.1394 0.1045 0.0836 At risk wave conditions Violent In-chamber Water Column Movement in an Oscillating Water Column (OWC) Wave Energy Converter Wave direction How does it work?

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Page 1: Violent In-chamber Water Column Movement in an Oscillating ... · In-chamber water behaviour : Oscillating water column is one of the most studied wave energy converters (WECs) which

Conclusions:• The WC is more likely to slosh during higher wave height

and less air resistance• The irregular wave condition is more likely to have a

sloshing compares to regular wave condition with the (significant) same wave height.

• Some amount of “sloshing” is not an uncommon situation and should be considered in design and performance assessment of an OWC chamber.

Acknowledgement: Indonesian Endowment Fund for Education (LPDP) for first author Ph.D study The “GWK OWCs” project was an EC Hydralab III access project led by University of

Edinburgh in collaboration with HR Wallingford, Second University of Naples, Queen’s University of Belfast, and the University of East Anglia

Krisna Pawitan, William Allsop, Tom [email protected]

1. Sea water trapped in a chamber with the bottom still connected to the sea

2. As the wave rises and falls, the water column inside the chamber oscillates up and down

3. This movement drives the air in and out of the chamber via power take-off mechanism

In-chamber water behaviour :

Oscillating water column is one of the most studied wave energy converters (WECs) which utilised the wave’s up and downmovement to generate electricity. The device excel among other WECs due to its simplicity and ability to be combined with aconventional breakwater, thus splitting the cost between energy generation and coastal defense. The water column insidethe chamber is often assumed to be well-behaved during operation in the design stage. A series of physical modelexperiments, however, proved that such condition is not always the case. It was found that in-chamber water movement(sloshing and slams) appears under certain wave condition. This study aims to characterise the type of sloshing occurs andthen identify the sea conditions under which the in-chamber water motion is more likely to occur.

Description:• Bc/L : characteristics width

• H/Hm0 : (significant) wave height

• Ao/Ac : opening:chamber area ratio

Symbols:• / : no video available

• ! : ceiling impact observed

• ^ : water level reached the ceiling

Closed 0.05 (0.06%) 0.1 (0.22%) 0.2 (0.88%) 0.3 (1.99%)

0.1 / /0.15 / / / /0.2 / / /

0.260.39 / / / /0.520.65 / / /0.78 !0.1 / / /

0.15 / / / /0.2 / /0.40.6 / / /0.8 ! !1 / / / ! /

1.2 / / / / !0.54 ! !0.81 / ! /1.07 / / / ! !1.61 / / / / !0.1 / / /

0.15 / / / /0.2 / / /