Changes between Version 119 and Version 120 of WikiStart

Sep 29, 2016, 12:14:58 PM (7 years ago)



  • WikiStart

    v119 v120  
    169169fixstr1_2809a: The goal is to increase the seeding and test the ADVs and UVP for less noise. A new stem ADV was mounted to reduce the noise. The UVP didn’t change in terms of noise issue, so the problem does not lie with the seeding density. Another suggestion was to move the UVP box back to the back bench to reduce interference from the electronics on the traverse. Minimal improvement was seen on the ADV profile. The seeding seems to be getting stuck in the inlet box behind the flow straightening baffles - this was visually observed by a buildup of foam in the inlet box.
     171fixapex_2809b: The siphons were moved up by 20 cm and the UVP 17 cm. The traverse was also moved to the second apex. The goal for this experiment was to take siphon and UVP data higher than 23.6 cm above the channel bed (previously not possible due to the siphon and UVP configuration), because we want to be able to draw velocity and concentration profiles fro 40 cm flow thickness. It was also intended to verify if moving the physical position of the UVP box would impact the data quality. Traverse moved to apex 2 position and siphon samples were taken every 1 minute after flow rate stabilized, for 1 minute sampling time (5-6 min, 7-8 min, 9-10 min).
     172When the flow was released a large cloud of seeding flowed through the channel as a gravity current (presumably seeding caught in inlet box from previous run) and the data on the ADV improved substantially. It was thus concluded that seeding is a viable solution to the noisy data problem (provided a reliable mechanism for seeding the flow, without it getting caught in the inlet box, can be devised). The other suggestion is to increase their distance further apart to avoid side lobe interference. UVP data remained noisy. It is speculated from pressing and !GoPro videos that surface waves are produced where the channel sides plunge under the free surface, and that this is the source of the noise in the UVP data.