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05/26/2021 Harbor Boat Day

Non-Float Hardware, 'Apparatus' tests conducted off Pier 160 around waters waters at Naval Base Point Loma.

Pic 05-26, 1: 2 fishing lines were attached to apparatus for safety.

Pic 05-26, 1: Close-up of picture 1.

Pic 05-26, 2: Team members Benny and Kristen ready start testing

Pic 05-26, 3: Approximate test site location. Satellite view from Google Maps

05/23/2021, Rigid Rod Connection, 'Splinted', Tests II

Final 2-Float 'Splinted' tests conducted at main test site, Canyonview Pool, UCSD. Extra long 3-hr session planned. 10 Separation Distances tested. 2-Float Splinted dataset completed

(Splinted Tests started 05/20/2021)

Pic 05-23, 1: A couple of extreme separation distances 37.5 cm + were tested. They required rigid rod extensions.

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Vid 05-23, 1: 2-Float Splinted drop.

05/21/2021, TRANSDEC TEST II

2nd test at TRANSDEC. Tests Done for rigid rod, 'splinted', configurations:

2-Float at various separation distances
2-5 Float lines 0-separation

(Splinted Tests started 05/20/2021)

Pic 05-21, 1: Team member, Kristen, reels up system after successful test

Pic 05-21, 2: 4-Float line 0-separation ascending towards drop site.

Pic 05-21,3-5: Left to right: 3-Float, 4-Float, Close-up of 5-Float all with zero separation. All 3+ sphere configurations were tested with 0 cm separation distance between buoys and used the splint to stiffen the system.

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Vid 05-21, 1: 5-Float 0-Seperation drop

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Vid 05-21, 2: 4-Float 0-Seperation drop

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Vid 05-21, 3: 3-Float 0-Seperation drop

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Vid 05-21, 3: 2-Float, 12.5 cm apart, dropping. A slight spin can be seen

05/20/2021, Rigid Rod Connection, 'Splinted', Tests

Fishing line connection between floats suspected of having too much give. Rigid Rod Connections, 'Splints' between floats introduced to reduce instability. Additionally adjusting separation distance is much easier with 'splint' than even Swivel-hooks. Testing-rate increased to 5-distances / 2-hr testing session.

Pic 05-20, 1: Team member Kristen set separation distance.

Vid 05-20, 1: Example of previous instability from fishing line connection.

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Vid 05-20, 2: 'Splinted' 2-Float drop.

05/03-13/2021, 2-Float Data

2-Float Dataset greatly expanded. 11 Separation distances tested in this period. The introduction of Swivel-hooks aided this. Separation distances could now be preset reducing prep-time during tests. Testing rate increased gradually to 4 distances / 2-hr period.

Pic 05-03-13, 1: Example of Swivel-hook

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Vid 05-03, 1: 2-Float drop.

04/30/2021, TRANSDEC TEST

Tests at deeper TRANSDEC, 11.3m (37 ft). Non-float hardware, 'Apparatus', tests done to determine drag contribution to overall system. Apparatus drag could than be isolated to derive true single spherical float drag coefficient. 1-float tests were also done to compare with Canyonview.

Pic 04-30, 1: System is dropped at hole in building platform over center of pool. Pictured left to right: Left, team observing drop. Right, team retrieving system after successful test. Bungee cord can be seen attached to fishing rod for Non-float hardware only test.

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Vid 04-30, 1: Apparatus drop. Much faster than system with floats.

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Vid 04-30, 1: 1-Float drop.

04/29/2021, 2-Float Data

Tests at deeper, 11.3 m (37 ft) special research pool TRANSDEC was scheduled for the next day. Non-float hardware only, 'Apparatus' tests will be conducted there. Without floats the system was too heavy and fast for Canyonview. System hits bottom before reaching terminal velocity. TRANSDEC was thought deep enough to allow 'Apparatus' only tests. Preparations for TRANSDEC were done on this day.

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Vid 04-29, 1-2: Retrieval line needed to be strengthened and reinforced to compensate for stronger sudden force felt due to heavier, faster Apparatus. Pictured left to right: Left, team member Kristen testing upgraded 60-lb rated fishing line on land. Right, Kristen testing bungee cord integrated to retrieval fishing rod as shock dampener.

04/19-26/2021, 2-Float Starts

2-Float testing began. 3 separation distances 1, 14, 32 cm were tested. Setting separation distance took substantial time. Eventually Swivel hooks will be implemented by 05/10 to substantially quicken the process.

Pic 04-19, 1: Full system layout. 2-float at 1 cm separation distance, dual sensors.

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Vid 04-26, 1: On 04-22 system was dropped too early and too high. Retrieval felt full weight of system, submerged buoyant force greatly reduced perceived weight. Excessive shocking loading snapped retrieval line. Line upgraded to 40-lb rated as a result. Pictured, team member Pedro testing upgraded line.

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Vid 04-19, 1: 2-Float, 1 cm separation distance drop.

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Vid 04-22, 1: 2-Float, 14 cm separation distance drop.

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Vid 04-26, 1: 2-Float, 32 cm separation distance drop. There was substantial raining on that day. Test persisted regardless.

04/12/2021, 2-Float Data

Dual sensor holders manufactured and integrated. Averaging 2 sensors values gives more reliable data.

Pic 04-12, 1: 4 sets of holders were produced by UCSD machine shop. Special thanks to the hardworking staff.

03/25/2021: 1st

This video shows a single trial in which data is collected for a drop of the single sphere configuration. This test was conducted using the first iteration of the retrieval system, which consisted of simply a wooden rod and fishing line.

Before fishing line was used to connect the orange float to the rest of the system, a more invasive rope connected them.

Computational Fluid Dynamics, CFD Sim

Shown above is the velocity mapping around 2, 3 and 5 inline spheres at the same freestream velocities. These images were created in a effort to explain why the 3-sphere configuration had the lowest drag coefficient of all the 2+ sphere configurations with 0cm separation.

04/18/2021: CFD Analysis Conducted on 2-Float Configuration

Two Sphere.avi

Although it doesn't capture the full effect of of Von Karman vortices, a slight oscillation is seen in the wake as the flow develops. However, Von Karman vortices are a steady state behavior and caused observable wobbles when the system was tested without the splint.

The three figures above show the velocity mapping over a plane through the center of the configuration. The top figure shows a separation distance of 1cm between the spheres, the middle figure is a 15cm separation, and the bottom figure has 30cm between spheres. Notice that as the separation increases, the second sphere moves further out of the wake of the first sphere. This helps illustrate the team's expectation that moving the second sphere into the wake of the leading sphere reduces drag. An other takeaway from these images is that the hardware does not have much of a wake compared to the spheres, meaning it will contribute relatively little drag to the entire system.

1-Float Configuration: General

1 Sphere Animation.avi

This animation shows pressure variation around the configuration with one sphere at Re = 73,984, which corresponds to a descent rate of about 49 cm/s. The animation was made using Solidworks Flow Simulation.

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