W2 Forum - Hydrodynamics

Evaluation of the vertical eddy diffusivity DZ

Sebastiano — Mon, 27 Mar 2023 20:01:33 +0000

I see that Dz is computed using the Reynold’s analogy, where Dz is related to the vertical eddy viscosity Az according to Dz=0.14Az This corresponds to considering a turbulent Prandtl number equal to Pr=Az/Dz=1/0.14~7, which is the molecular Pr of water. I was expecting a Pr~1, which is the turbulent Pr for water. Why the factor 0.14 is used instead? Thank you

Forums:

Hydrodynamics

Bathymetry section generation for river or reservoir with an island

Hanief — Fri, 16 Dec 2022 09:07:42 +0000

How would one go about generating cross sections for a river/reservoir in which there is an island or two. One island is in the main river channel and one off center of the channel Is it possible to resolve the cross section by subtracting the volume of the island? This would make this cross section's volume less and surely this will affect the hydrodynamics and velocities for the cross section before and after The islands are quite sizeable and almost 5-15% of the volume of water. Any suggestions would be appreciated

Forums:

Hydrodynamics

Particle tracking questions

Dongyu — Thu, 21 Nov 2019 18:46:48 +0000

I am trying to run particle tracking example in CE-QUAL-W2. But I got an issue here.

The particles were initialized uniformly at the first segment that has water and were able to transport for a few steps. But after that, the particles were blocked at one segment that is far from the downstream gate. It seems that the particles hit a wall. They were either attached or bounced back to upstream. But the segment is not a wall and has horizontal velocity along it. Can anyone give me a hint of what is going on here?

I am very new to this model and the questions may sound stupid. Your answers are important to me. Thank you in advance. Please let me know if you need any additional info.

Forums:

Hydrodynamics

A error in W2Pre running

jparsa — Tue, 02 Jul 2019 09:37:50 +0000

Hi When I am running W2Pre, an error occurs. The error is "Julian date .000 <= previous date". Could anyone help me? Thanks a lot Parsa

Forums:

Hydrodynamics

Question about CE-QUAL-W2 daily output.

Ramon — Wed, 05 Jun 2019 12:12:36 +0000

Dear Professor Wells and Professor Berger My name is Ramon Pinto de Barros, I'm a Master degree student at the University of Brasília, Brazil - Postgraduate Program on Environmental Technology and Water Resources - Department of Civil and Environmental Engineering. I've been using the CE-QUAL-W2 model for almost an year, making an effort to turn it useful for simulations of the most important reservoir of the Brazilian Federal District, the Descoberto Reservoir, used to supply water for human consumption of 60% of the population (1.8 million people). I have developed a python language tool for automatic model calibration and the application has been satisfactory. I may say that the model has been simulating greatly Temperature and Water levels, However, if possible, I would like to clarify a question about the model output data. I would like to have a better understanding related to the model output "day-by-day data". This is very important for our understanding of the model output and the Reservoir as well. I'm working mostly with monthly gauged data. Only the climate data are daily through the entire series. Consequently, one of the goals of my work is to understand what is happening to Descoberto Reservoir in the days that we don't have available data (observed data). As the climate data is hourly, I have doubts about the results generated by the model.. EG: Would the result of JDAY 100.0 be from the start of the day (00:00am), or an averaged data from the entire day? I may tell that the climate here in Brasilia may vary from 10ºC to 35ºC in a single day-night cycle, so, even though the model is not outputting hourly, it'd be great to know if my understanding related to the model outputs is correct. I am simulating temperature for calibration purposes. Thanks in advance.

Forums:

Hydrodynamics

Horizontal Velocity Time Series

Sofia — Wed, 16 Jan 2019 20:18:05 +0000

Hello! I'm running a W2 model for a lake in Brazil that has been calibrated for hydrodynamics and temperature. However, I want to output the time series for horizontal velocity, in order to get Reynalds medium values for the lake, but when i try to extract them it returns lots of "-999" values. What does this means? Usually "-999" indicates lack of data, but how do I correct this? Cause there's no indication of any running error.. Any help would be great..

Forums:

Hydrodynamics

weird results for small layer height

Allie — Mon, 10 Sep 2018 18:03:35 +0000

Hello, I'm simulating a lake that's 9m deep and intermittently stratified. I decided to explore the effect of refining the layer height (DZ). For DZ=0.3m, I get reasonable results: internal waves along the thermocline cause temperatures to fluctuate throughout the water column for the entire 3-month duration of the simulation. However, if I reduce to DZ=0.1m, temperatures flatten out, i.e., stop varying in time, about half-way through the simulation in the bulk of the water column -- only the surface temperature fluctuates at all after this point. Is there some way a small layer height could result in numerical errors that cause effects like I'm seeing? Thanks, Allie

Forums:

Hydrodynamics

Internal Wave Simulation

Tyler — Mon, 27 Aug 2018 06:31:18 +0000

Hello everyone, I am a new CEW2 user and am trying to determine if this simulation scenario is appropriate. I've essentially inherited a calibrated CEW2 model of river-reservoir system from an elder research student who was primarily focused on water temperature. We collected some in-situ data which suggests small-scale internal wave activity which is primarily influenced by the hydropeaking of the dam. I'd like to try and model this phenomenon, and given that I have a base-line model of the system already I was wondering if CEW2 can represent the physical mechanisms well enough for analysis of the in-situ data. In general the site favors a 2-D laterally averaged model, but I haven't found much research online analyzing internal waves with CEW2. Is there any reason this wouldn't work? Any suggestions or advice would be much appreciated. Thanks.

Forums:

Hydrodynamics

withdrawal and bottom layer

Amandine — Tue, 07 Aug 2018 07:21:55 +0000

Dear all, I am a new user of W2, I have au model with a withdrawal. I want that withdrawal stop when the water surface elevation is below a fixed level. I checked that the value of KBWD is good. (I fixed KBSTR too, but I do not know if it is necessary). However the withdrawal continues even if the water surface elevation is below a fixed level. Do you know what could be the problem. Many thanks

Forums:

Hydrodynamics

shade reduction factor

Chenxi — Sat, 21 Jul 2018 12:32:29 +0000

Dear all, currently I calibrated the water temperature in a Germany reservoir. I found that the simulated water temperature in winter is much lower than the observation. I try to change the wind factor, ice parameter, light extinction factor and so on. Finally I found that if I increased the "DynSh" to higher than 1 in the shade file (e.g. 1.2), the results in winter is much better than before. However, in the manual, it is said that the DynSh should be between 0-1.... I want to know that whether it is an approiprate way to increase the DynSh higher than 1? Does the DynSh is just like the data in wsc file which is only a simple multiplied factor? Many thanks for the kind help!!

Forums:

Hydrodynamics