HY8:Limitations: Difference between revisions

From XMS Wiki
Jump to navigationJump to search
No edit summary
Line 13: Line 13:


==Hydraulic Jumps==
==Hydraulic Jumps==
HY-8 does not attempt to show the location of a hydraulic jump in the culvert profile.  Additionally, if more than one flow type exists for the culvert profile, HY-8 does not attempt to show multiple profiles.
Hydraulic jump computations are supported in HY-8 7.3 and later versions.
 
NOTE: The user should be aware that when the tailwater elevation exceeds the elevation of the top of the culvert outlet, HY-8 assumes that the barrel flows full at the outlet and reports an outlet velocity corresponding to full flow.  A more detailed description of this limitation is given in the Help document under the limitations topic.


==Culvert Types==
==Culvert Types==
The following types of culverts are still not available
Previous versions of HY-8 did not fully support CON/SPAN culverts, HDPE culverts, or culverts installed with a natural stream bed as the bottom.


There are several culvert types, such as CONSPAN or HDPE plastic, which were unsupported in MS-DOS HY-8 and will continue to be unsupported in HY-8 version 7.0.
CON/SPAN (Concrete Open-bottom Arch) culvert types are supported in HY-8 7.3 and later; HDPE plastic culvert types are supported in HY-8 version 7.1 and later.


Partially buried culverts or culverts with natural stream bottoms remain unsupported in HY-8 version 7.0.
Partially buried culverts or culverts with natural stream bottoms were supported in HY-8 version 7.1 and later versions.


==Broken Back Culverts==
==Broken Back Culverts==
Culverts with multiple slopes (broken back) and adverse slopes remain unsupported.
Culverts with multiple slopes (broken back) and horizontal/adverse slopes are supported in HY-8 7.3 and later versions.


{{HY8Main}}
{{HY8Main}}

Revision as of 19:52, 15 December 2011

Limitations

Computed outlet velocity and tailwater elevation

The user should be aware that when the tailwater elevation exceeds the elevation of the top of the culvert outlet, the barrel may or may not flow full at the outlet. HY-8 determines a water profile using the direct step method in each direction and the sequent depth associated with each of the steps. If the sequent depth associated with the forward profile matches the depth along the backward profile through the culvert, a hydraulic jump occurs and the length of the jump is calculated from that location. Since the lengths of jumps have not been tested for all culvert sizes and slopes, only a limited set of equations are available for computing the lengths of jumps in HY-8. More information on the jump length computations is available in the section of this manual that describes hydraulic jump computations. A water surface profile for this case is shown below.


HY8image59.png


In this case, the hydraulic jump length computed by HY-8 may or may not be correct since the equation used to compute hydraulic jump length is for box culverts only, but is applied to all the other possible HY-8 culvert shapes. If a hydraulic jump occurs inside the culvert and the end of the hydraulic jump is located outside the culvert, HY-8 assumes the hydraulic jump occurs outside the culvert and a hydraulic jump is not shown in the profile. If both the beginning and end of the hydraulic jump occur inside the culvert barrel, the hydraulic jump is shown in the profile and is reflected in the profile computations, as shown in the image above.

Hydraulic Jumps

Hydraulic jump computations are supported in HY-8 7.3 and later versions.

Culvert Types

Previous versions of HY-8 did not fully support CON/SPAN culverts, HDPE culverts, or culverts installed with a natural stream bed as the bottom.

CON/SPAN (Concrete Open-bottom Arch) culvert types are supported in HY-8 7.3 and later; HDPE plastic culvert types are supported in HY-8 version 7.1 and later.

Partially buried culverts or culverts with natural stream bottoms were supported in HY-8 version 7.1 and later versions.

Broken Back Culverts

Culverts with multiple slopes (broken back) and horizontal/adverse slopes are supported in HY-8 7.3 and later versions.