paul_ollett

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About paul_ollett

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    www.HYDRALINC.com
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  1. Hi Francis, Sorry for the late reply. My notifications have not been working on the forum. Please find attached the document requested. Hope it all makes sense. Regards, Paul. www.HydraLinc.com Catchment Slope Calculation - Vertical Mapper.pdf
  2. Hi Phil, Sorry, my post may not have been very clear. My real question is can you do this in ArcGIS? I don't think it is possible in Arc (everyone I've asked who is an Arc user says no). No applause just yet mate.... ;-) Cheers Paul.
  3. Hi there, In VM it is possible to plot a number of grids on a long section or cross section in a waterway, for example, a DEM with several flood profiles (existing vs. developed cases, or, multiple AEPs). It this possible in ArcGIS? Any pointers would be much appreciated..... Kind regards, Paul.
  4. Hi Mark, Sometimes when draining a 2D area using a special structure (eg, a basin with a multi-staged outlet) I've used a 1d pump. They are nice in that you can specify your own Head-Discharge relationship. The old style 1d pumps don't record outputs such as discharge with time, however the new pumps in the latest version of TUFLOW may record more outputs. The latest tutorials also have an example of a pump set-up. Regards, Paul.
  5. Hi Eric, I've not used the GPU version of TUFLOW before. One thing you could do is apply a really high IL (eg, 1000mm) in the Materials file, but set ILs in the 2d_sa_rf to zero, and see if the model generates any runoff. Visa versa. This way you will know which one handles rainfall losses. Sounds like you're doing some interesting work Kind regards Paul.
  6. Hi Claire, I am by no means an expert on this topic, but I do have one experience. (note this was 3 years ago and I had only been using TF for a short time...so I could be completely wrong!). I once set up a laboratory model in TF to test the performance of a fine scale hydraulic structure. Basically the flume I was modelling was about 400mm deep, and I used a grid cell size of 0.1m. For TF to replicate the lab result, I had to turn-off the sub-scale turbulence model (for a grid orientated parallel to the flume). For a grid at a 45 degree angle to the flume I had to introduce a minor amount of constant viscosity for stability. (increasing Manning's roughness did not provide any dampening). The commands I used for the 45 degree grid in the TF control file were: Viscosity Formulation == SMAGORINSKY Viscosity Coefficients == 0.00, 0.014 ! <smag, cons> !!! Viscosity Coefficients == 0.2, 0.1 !Tuflow default {0.2, 0.1} | <smag, cons> I'm not sure what your application is, but my recommendation is a sensitivity analysis. If for example you are looking at providing scour protection around piers, then a lower viscosity may give you higher velocities. Hopefully this will not translate into significant additional construction costs. Cheers Paul www.hydralinc.com
  7. Hi there, I am collating some standard references for flow (flood) control and measurement structures, for example, sluice gates, radial gates, ogee spillway, broad crested spillway, and various weirs (lateral, labyrinth, v-notch, rectangular notch, flumes, etc). I have a few well known standards or manuals from the US, for example: USBR Design of Small Dams 1987 USBR Water Measurement Manual 2001 HEC RAS Reference Manual Floodplain Modelling Using HEC RAS (Bently) I wanted to ask if anyone knew of similar industry standard approaches or publications for the same in other countries, especially the UK? Cheers, Paul.
  8. Hi there, I saw this post from a few years back re import of XP SWMM hydrographs into TF: http://www.tuflow.com/forum//index.php?showtopic=962&hl=%2Bxp+%2Bswmm It discusses the use of the XP utility interfaceutils.exe which can convert hydrographs from an XP hydrological output file (.syr) to .csv. Just wondering, is this still the most efficient way of going about getting XP SWMM hydrographs into TUFLOW? I'm flying a bit blind as I am not familiar with XP SWMM, but need to sort out an efficient method of extraction for future TUFLOW models. I noticed the TF manual refers in Table 4.28 to: XP .int and .ext interface formats. Cheers Paul.
  9. Hi all, When modelling bridges in a 1D scheme (eg, HEC RAS), flow separation under and over a bridge is often replicated using the orifice and weir equations. In TF using the LFCSH method, a cell's width is decreased linearly in the vertical to account for the overall proportions of blockage (eg, piers + deck + guard rail, etc). This will not necessarily account for all energy loss due to a submerged superstructure. When flood levels reach the bridge soffit (=> L1_Obvert) I would expect a significant increase in form loss (L1_FLC to L2_FLC). I wanted to ask if anyone had investigated this, to provide some preliminary guidance for simple bridge configurations? I do suspect this to be a complicated topic (for example, different energy loss coefficients may be needed depending on cell size). Regards, Paul.
  10. Hi Paul,

    This is Khairul. It seems you left GCCC as well. Where are you now mate? I am at LCC. Cheers - Khairul

  11. Hi Sam, The Queensland Urban Drainage Manual has a section on grates, where guidance is expressed in terms of energy loss coefficients. You should be able to use these coefficients directly in Estry, ie, the Entry_Loss and Exit_Loss attributes. If your structure is acting under inlet control, then you will need to back calculate the values for the Height_Cont and Width_Cont coefficients. Definitely they will be less than the values recommended in the TF Manual or in Henderson. Cheers, Paul.
  12. Hi there, I’ve been running some 'direct rainfall' urban flood models, and calculating residual depths once the catchment has fully drained. Basically I’m coming up with average residual depths of around 30mm over a catchment, for different catchment gradients and land-uses. I do believe this initial loss due to the depressions in the DEM is exaggerated, due to grid or ALS resolution, and also discontinuities or blockages of sheet-flow paths due to the DEM generation process. I’m just in the process of thinking through the cleanest way to account for this initial loss due to depressions in the DEM. I initially thought of a process such as subtracting the 30mm from the ARR type IL values in the TUFLOW Materials File(.tmf). This however starts to get messy (negative ILs), is hard to audit, and may require rainfall data to be adjusted. The best method I can think of is to run an initial simulation for say 6 hours, applying 30mm rainfall over the first hour to fill depressions, then waiting until the catchment drains. This would be with no IL or CL in the tmf file. Then, create a flood surface at t=6 to use as part of a restart or initial condition for the real flood simulation. This way, adjustments of the ‘standard’ IL and CL values in the tmf are not needed, and these should still be comparable to test book values such as in ARR. It’s interesting that this initial loss component due to depressions in the DEM will vary depending on the grid interpolation method (eg, TIN, IDW), and even cell size (larger cells apply more smoothing and possibly contain less depressions). Instead of trying to reduce the IL values in the tmf file, I think the second method could work well for any DEM scenario. Just wanted to ask if anyone had looked into all this in detail. Are there any other techniques being used? Cheers Paul.
  13. Hi there, Is it possible to write out model results part way through a simulation for checking? I’m also interested in 1D results for bridges and cross road drainage, and plot outputs to check stability of structures. Ideally what I would like to do is pause the model, write out results, copy results to another directory for processing and checking, and if all is well to restart the model. Cheers, Paul.
  14. Hi Nick, Could you try using this equation: Q=C*A*(2g(H-C*D))^0.5 C = coefficient (rounded edge = 0.8; square edge = 0.6) A = Area H = headwater level - pipe invert (upstream depth) D = Depth of water in barrel (diameter in your case) See if that gets you closer... Cheers Paul.
  15. Hi Nick, If the orifice is 'free outflow' (inlet control), for your hand calculation, how did you measure the headwater depth above the orifice? Did you measure down to the centre of the orifice, or down to the obvert of the orifice? If just down to the obvert, this could explain the lower discharge with the hand calc. Cheers Paul.