156A Week 9

• What has been done in the past week

Discussion and decision made on primary design using PVC pipes, low density foam, strengthening rods, a base support collar, and supporting buttresses

Made initial search for the necessary hardware

• Feedback from meeting with sponsor

Discussed the kelp range, which should be about 10m to 30m, preferably should cover 75- 80%. The spar is to have a height of about 10m (33 feet).

There are two forms of motion to consider, which is steady water current associated with the tides and the oscillatory motion of underwater waves. Current is the main concern underwater because flow velocity can be a lot faster.

Typical wave height during the summer (when the spar would be deployed) is an average of about 1.5m with a period of approx. 10 seconds. Steady tide flow has an average velocity of about 30-40cm/s

Temperature is not an issue because typical temperature is 50- 60 degrees.

Current problems with the design right now

• Surface waves move the whole spar so must decide the best way to anchor it to the seafloor which can be achieved using weights or flooring nails

• Since the spar has flexibility, only reinforcing certain points along the spar will cause different modes of bending along it and can cause failure with strong enough currents.

• Metals used have to be compatible to avoid significant corrosion, can be overcome by using only one type of metal throughout, preferably Galvanic Potential metal like 316 stainless steel

• The spar is about 8-12m long in height and there will be 5 ADV attached to the spar pointing different directions to obtain the most accurate readings.

• Feedback from last meeting with instructor

It was pointed out that we should know what the conditions are for our working environment such as depth of water and consider the importance of wave motion vs. water flow

How will the instrument make its measurements? The probe that has the sensors measures the velocity and orientation is not critical

• List your current concern according to the importance

• Conditions in water. Must derive flow and wave equations to simulate the spar’s response to these types of motion. This is critical as we do not want the spar to bend and crack or break, whether it be at the bottom support or in the middle when support structures are to be attached

• Corrosion: a big issue with any instrument deployed in the ocean. Need to make sure the materials used account for this. PVC has great corrosion resistance and metals used must be the same type to avoid making what is essentially a battery that will cause major corrosion when two different metals are in contact.

• What is the next step of your project

• To come up with a better design that is more rigid. The current idea is to use some type of supporting rods running up the sides of the PVC pipe spar to strengthen it so that the support arms(or buttresses) do not cause bending modes.

• Figure out the most efficient way to assemble the spar. Ideally, we want to create something that can be carried in a mid-sized boat and can be assembled out at sea. We also aim to design it so that it can be easily rearranged at will, such as switching the location of an ADV or replacing a battery housing, etc.

• Figure out how to attach the ADVs and where, since it’s in the kelp. We do not want the probe sensors to be sticking out too far so that it does not get tangled in kelp. Also, if a sensor is directly opposite of the flow coming across the spar, it will not take a good reading as it will be in the wake of the flow so must have them coming out in different orientations to account for this

• Installation of the spar, secure the base of the spar. The current idea is to machine (or find) a collar with supporting legs to hold the spar rigidly at the bottom.

Tasks:

• Search for necessary hardware such as pipes, pipe connectors or couplings, and structural materials. (Erik Zamarripa and Eliran Lenard) [pipe connector image is shown below].

Some possible candidates have been found but still looking for the most cost efficient.(Erik)

• Derive the flow and wave equations describing the underwater motion (Erik Z.and Horim Yu)

• Assemble and manufacture the prototype for preliminary testing (Erik Z. and Eliran Q.L, Ayesha Riaz)

• Design and performing FEAs on Mooring structure (Eliran Lenard and Erik Z.)

• Drive to certain plumbing stores to find appropriate PVC pipes, connectors, nuts, screws, etc and buy equipment (Eliran Lenard, Erik Z, Ayesha Riaz)

• Perform hand calculations for certain forces applied on Structure

Revision 1 and 2 is shown below. After speaking with professor Pawlak November 30, 2021, there was a better understanding/clarification of what was wanted from him. Still working on design at the moment. Should be completed this week.