HY8:Outlet Control Computations: Difference between revisions

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Outlet control means that the amount of water the culvert barrel can carry is limited by the barrel and/or tailwater conditions downstream.  As a result, the flow in the barrel is subcritical, and the energy equation may be used to find the upstream headwater depth.  Several flow profiles are possible and are shown below and on page 32 of HDS-5.  The following correlations apply to HY-8:  Type A in HDS-5 is Type 4 in HY-8, Type B in HDS-5 is Type 3 in HY-8; Type C in HDS-5 is Type 6 in HY-8, Type D in HDS-5 is Type 7 in HY-8, and Type E in HDS-5 is Type 2 in HY-8.  Descriptions of these flow types may be found in HY-8 by selecting the “Flow Types” button from the Culvert Summary Table.  The logic for determining flow type and the headwater elevation due to outlet control is shown below from the HY-8 help file.
== Outlet Control Flow Types ==


   
Outlet control means that the amount of water the culvert barrel can carry is limited by the barrel and/or tailwater conditions downstream. As a result, the flow in the barrel is subcritical, and the energy equation may be used to find the upstream headwater depth.  Several flow profiles are possible as are shown below and as described in HDS-5.  HY-8 flow types 2, 3, 4, 6, and 7 are all outlet control flow types and are shown in the figure below.  The various flow type properties may be found in HY-8 by selecting the '''Flow Types''' button from the ''Culvert Summary Table'' and are shown [[#HY-8_Flow_Types|below]].


[[Image:HY8image38.gif]]
[[Image:OutletControlFlowTypes.png|450px]]


== Outlet Control Computations ==


==='''STEP'''===
The logic for determining flow type due to outlet control is shown in the figure below: {{only in print|(Zoom in or click on this image to see it more clearly)}}
#Compute critical depth (dco)
#Compute normal depth (dno)
#Compute fullflow if nomograph solution assumed "6-FFt or FFc".
#If dco > rise, assume fullflow "6-FFc".
#:If oh < ih, compute S2 curve, "5-S2n" if submerged, else "1-S2n"
#If dco < dno, assume mild slope.
#:A.  If tailwater (twh) >= So(L) + rise, compute fullflow "4-FFt".
#:B.  If twh >= rise, outlet submerged, assume inlet unsubmerged
#::i.  Pipe flows partially full, compute M1 curve "3-M1f".
#:::  Length of curve = L - (twh - rise) / So
#:::  Outlet DEPTH = rise.
#::ii.  If inlet submerged, full flow "6-FFt".
#:C.  If twh >= dco, outlet depth = twh.
#::i.  If twh is >= dno, calculate M1 curve "3-M1t"
#:::  If depth = rise, fullflow from that point. "7-M1t"
#::ii.  If twh is < dno, calculate M2 curve "3-M2t"
#:::   If depth = rise, fullflow from that point. "7-M2t"
#:D.  If twh is < dco,  outlet depth = dco.
#::i.  Calculate M2 curve "2-M2c".
#:::  If depth = rise, fullflow from that point. "7-M2c"
#If dco >= dno, assume steep slope.
#:A.  If twh is >= So(L) + rise, assume fullflow "4-FFt".
#:B.  If twh is >= rise, outlet submerged, assume inlet unsubmerged.
#::i.  Steep channel-hydraulic jump forms
#::ii.  Calculate fullflow headwater (oh) "6-FFt or FFc"
#::iii.  If oh < rise, then inlet is unsubmerged.
#:::a.  Length full = (twh - rise) / So
#:::b.  Calculate S1 curve "1-S1f".
#::::  If oh >= rise, inlet submerged "5-S1f".
#:::c.  If oh is < twh, tailwater drowns out jump.
#::::  Calculate M1 curve "3-M1f".
#::::  If oh >= rise, inlet submerged "5-M1f".
#:C.  If twh is < rise, outlet is unsubmerged, inlet can be either.
#::i.  Headwater (oh) = fullflow headwater
#:::  Calculate S2 curve "1-S2n" for outlet depth.
#:::  If oh >= rise, inlet submerged "5-S2n"
#::ii.  If twh > headwater, tailwater drowns out jump.
#:::  Calculate M1 curve "3-M1t".
#:::  If culvert flows part full, "7-Mit".


{{hide in print|[[Image:OutletControlFlowchart.png|650px]]}}
{{only in print|[[Image:OutletControlFlowchart.png|x800px|center]]}}


     
This flowchart uses the following terms:


'''HJ''' = Check for [[HY8:Hydraulic Jump Calculations|Hydraulic Jumps]]


==='''OUTLET CONTROL 'FIXES' FOLLOWING HY-8 6.1'''===
'''Full flow''' = Check if the culvert is flowing full


:    KE = KE(IC)
'''TWH''' = Depth of the tailwater from the invert of the tailwater channel at the culvert outlet
:    A7 = 64.4: A8 = 29: A1 = 1: A2 = .25: A3 = 2: A4 = 4 / 3: A5 = 3.14159: A6 = 4
:    SELECT CASE PSHAPE 'CRITICAL DEPTH
:    CASE 2
::          GOSUB 6210
:    CASE 1, 3 TO 10
::          GOSUB 6220
:    END SELECT
:    GOSUB 6280    'NORMAL DEPTH
SELECT CASE WSP$  '***added 3.1, 4.4 changed wsp
CASE "F"
:    GOSUB fullflow
CASE ELSE
:    SELECT CASE DCO  'changed to DCO from DNO 4.5
:    CASE IS >= RISE'If Yn = to RISE, assume full. ***added >.95 3.3, revised 4.5
::          WSPTYPE$ = "FFc"
::          GOSUB fullflow
::          IF (IH + I1E) > (OH + I1E) THEN
:::              WSPTYPE$ = "S2n": GOSUB S2CURVE
:::              IF IH > RISE THEN FLTYPE = 5 ELSE FLTYPE = 1 'added 3/05 to correct FLTYPE=6
::          END IF
:    CASE IS < DNO 'Mild slope
::          SELECT CASE TWH
::          CASE IS >= S0 * L + RISE  'Pipe flows full
:::              GOSUB fullflow
::          CASE IS >= RISE  'Outlet submerged, Inlet unsubmerged
:::              'Pipe flows partially full, M1 Curve
:::              D0 = RISE
:::              LCURVE = L - (TWH - RISE) / S0: LADJ = LCURVE
:::              GOSUB M1CURVE  'M1 Profile
:::              DL = RISE: GOSUB SectionProp: VOUT = Q / AC: DOUT = RISE '***added 3.3
:::              FLTYPE = 3: WSPTYPE$ = "M1f"
::          'Inlet unsubmerged, outlet unsubmerged
::          'If Inlet is submerged FLTYPE = 7 is returned
::          CASE IS >= DCO
:::              SELECT CASE TWH
:::              CASE IS >= DNO
::::                    FLTYPE = 3: WSPTYPE$ = "M1t"
::::                    D0 = TWH: LADJ = L
::::                    GOSUB M1CURVE: DL = TWH: GOSUB SectionProp: VOUT = Q / AC: DOUT = TWH
:::              CASE IS < DNO
::::                    FLTYPE = 3: WSPTYPE$ = "M2t"
::::                    D0 = TWH '**3.3 changed from DO=DCO
::::                    GOSUB M2CURVE: DL = TWH: GOSUB SectionProp: VOUT = Q / AC: DOUT = TWH
:::              END SELECT
::          CASE IS < DCO
:::              FLTYPE = 2: WSPTYPE$ = "M2c"
:::              D0 = DCO: GOSUB M2CURVE: DL = DCO: GOSUB SectionProp: VOUT = Q / AC: DOUT = DCO
::          END SELECT  'TWH for mild slope
:    CASE IS >= DNO 'Steep slope
::          SELECT CASE TWH
::          CASE IS >= S0 * L + RISE
:::              GOSUB fullflow
::          CASE IS >= RISE  'Outlet submerged, Inlet unsubmerged
:::              'STEEP CHANNEL-HYDRAULIC JUMP FORMS
:::              IF TWH < DNO THEN TWH = DNO '***3.3 moved
:::              GOSUB fullflow
:::              IF OH < RISE THEN
::::                    LFULL = (TWH - RISE) / S0
::::                    D0 = RISE: LCURVE = L - LFULL
::::                    GOSUB S1CURVE
::::                    IF OH + I1E > TWH + I2E THEN
:::::                        FLTYPE = 1: WSPTYPE$ = "S1f"
::::                    ELSE
:::::                        FLTYPE = 3: WSPTYPE$ = "M1t"
:::::                        D0 = RISE: LADJ = L 'Tailwater drowns out jump
:::::                        GOSUB M1CURVE
::::                    END IF
:::              END IF
::        CASE IS < RISE  'Outlet unsubmerged, Inlet unsubmerged & submerged
:::              'OH = IH deleted 12/05 (should check OH from M1 with IH
:::              'IF OH + I1E > TWH + I2E THEN
:::              '        'GOSUB fullflow 'added 45 to revise plot, deleted 61
:::              '        FLTYPE = 1: WSPTYPE$ = "S2n"
:::              '        GOSUB S2CURVE
:::              'ELSE  'Tailwater drowns out jump
:::              '        FLTYPE = 3: WSPTYPE$ = "M1t"  'M1 profile
:::              '        D0 = TWH: LADJ = L
:::              '        GOSUB M1CURVE: DL = TWH: GOSUB SectionProp
:::              '        VOUT = Q / AC: DOUT = TWH
:::              '        'If culvert flows part full FLTYPE = 7 is returned
:::              'END IF
:
:::              IF TWH <= DNO THEN
::::                    FLTYPE = 1: WSPTYPE$ = "S2n"
::::                    GOSUB S2CURVE
:::              ELSE  'assume Tailwater forces jump calculate M1
::::                    FLTYPE = 3: WSPTYPE$ = "M1t"  'M1 profile
::::                    D0 = TWH: LADJ = L
::::                    GOSUB M1CURVE: DL = TWH: GOSUB SectionProp
::::                    VOUT = Q / AC: DOUT = TWH
::::                    'If culvert flows part full FLTYPE = 7 is returned
::::                    IF IH > OH THEN 'M1 does not control calculate S2
:::::                        FLTYPE = 1: WSPTYPE$ = "S2n"
:::::                        GOSUB S2CURVE
::::                    END IF
:::              END IF
:::              IF OH >= RISE THEN FLTYPE = 5
::          END SELECT 'TW for steep
:    END SELECT 'DNO
END SELECT 'HDS5
:    WSPTYPE$(0, 0) = WSPTYPE$
:    RETURN


'''twOutletDepth''' = Depth of the tailwater from the invert of the culvert at the culvert outlet.  If the culvert is buried, this value is taken from the top of the embedment material.


'''IH''' = Inlet control headwater depth measured at the inlet invert of the culvert


'''OH''' = Outlet control headwater depth measured at the inlet invert of the culvert


{{HY8Main}}
'''RISE''' = Height of the culvert.  If the culvert is buried, this value is taken from the top of the embedment material.
 
'''Inlet Depth''' = The depth computed at the entrance to the culvert using the direct step profile computation method
 
'''Critical''' = The critical depth in the culvert
 
'''Normal''' = The normal depth in the culvert
 
{{WMS:HY-8 Flow Types}}
 
 
[[Category:HY-8 Analysis|O]]

Latest revision as of 15:14, 7 October 2016

Outlet Control Flow Types

Outlet control means that the amount of water the culvert barrel can carry is limited by the barrel and/or tailwater conditions downstream. As a result, the flow in the barrel is subcritical, and the energy equation may be used to find the upstream headwater depth. Several flow profiles are possible as are shown below and as described in HDS-5. HY-8 flow types 2, 3, 4, 6, and 7 are all outlet control flow types and are shown in the figure below. The various flow type properties may be found in HY-8 by selecting the Flow Types button from the Culvert Summary Table and are shown below.

OutletControlFlowTypes.png

Outlet Control Computations

The logic for determining flow type due to outlet control is shown in the figure below:

OutletControlFlowchart.png


This flowchart uses the following terms:

HJ = Check for Hydraulic Jumps

Full flow = Check if the culvert is flowing full

TWH = Depth of the tailwater from the invert of the tailwater channel at the culvert outlet

twOutletDepth = Depth of the tailwater from the invert of the culvert at the culvert outlet. If the culvert is buried, this value is taken from the top of the embedment material.

IH = Inlet control headwater depth measured at the inlet invert of the culvert

OH = Outlet control headwater depth measured at the inlet invert of the culvert

RISE = Height of the culvert. If the culvert is buried, this value is taken from the top of the embedment material.

Inlet Depth = The depth computed at the entrance to the culvert using the direct step profile computation method

Critical = The critical depth in the culvert

Normal = The normal depth in the culvert

Inlet control means that the amount of water the culvert barrel can carry is limited by the culvert entrance. Flow passes through critical depth at the culvert entrance and is supercritical in the barrel. There are several flow profiles possible, HY-8 simulates so-called Type A, B, C, and D conditions as shown below and as described in HDS-5. These profiles are known as Type 1 (A, C) and Type 5 (B, D) within HY-8. The various flow type properties may be found in HY-8 by selecting the Flow Types button from the Culvert Summary Table and are shown below. Because the flow in the barrel is supercritical, outlet losses and friction losses are not reflected in the headwater elevation. The headwater elevation is a function of the entrance size, shape, slope, and culvert type. The computed inlet control headwater elevation is found by accessing the results of scaled physical model tests. The logic for determining what inlet flow control type prevails is shown below (from the original HY-8 help file).


InletControlFlowTypes.png


Inlet Control Logic

Determine Applicable Inlet Control Equation

  1. IF circle or box with IMPROVED INLETS then use INLET equations.
  2. For Straight (previously called conventional) INLETS
    A. If Q is < Q at .5D, then assume LOW FLOW INLET CONTROL:
    i. calculate CRITICAL DEPTH (DCO)
    ii. calculate Section Properties
    iii. VH = (Q / AC)^2 / 64.4
    iv. IH = DCO * LMULT + (1 + KELOW) * VH * VHCOEF
    IF no Depression THEN IHI = IH + I1E
    For Depression, HF = IH and check head on CREST.
    B. If Q > Q at .5D, but < Q at 3D, then use INLET REGRESSION EQUATIONS.
    C. If Q > Q at 3D, then assume HIGH FLOW INLET CONTROL.
    i. IH = (Q / CDAHI)^2 + .5 * RISE
    ii. IF no Depression THEN IHI = IH + I1E
    For Depression, HF = IH and check head on CREST.

Inlet Regression Equations (Q between Q at 0.5D and Q at 3D)

  1. CIRCULAR
    A. See Straight inlet equations
    B. SIDE TAPERED ELLIPTICAL TRANSITION, THROAT CONTROL
    ZZ = Q / SQR(RISE ^ 5), Y = LOG(ZZ) / 2.30258
    i. IF n < .015 THEN SMOOTH PIPE IMPROVRD INLET.
    ii. If n >=.015 then ROUGH PIPE IMPROVED INLET.
    iii. Calculate THROAT CONTROL
    iv. Calculate FACE CONTROL
    v. IF Depression Then CW = CWF, calculate CREST control.
    C. SIDE TAPERED RECTANGULAR TRANSITION or SLOPE TAPERED
    i. Calculate THROAT CONTROL
    ii. Calculate FACE CONTROL
    iii. IF Depression Then CW = CWF, calculate CREST control.
  2. BOX CULVERTS
    A. See Straight inlet equations
    B. SIDE TAPERED RECTANGULAR TRANSITION or SLOPE TAPERED
    i. Calculate THROAT CONTROL
    ii. Calculate FACE CONTROL
    iii. IF Depression Then CW = CWF, calculate CREST control.
  3. PIPE ARCHES AND ELLIPSES
    A. See Straight inlet equations
  4. IRREGULAR SHAPE
    A. See Straight inlet equations


Straight Inlet Equations

  1. For IRREGULAR shape, X = Q / (AC * SQR(RISE))
    IF X <= .5 THEN IH = (A(1) * (X / .5)) * RISE
    ELSE IH = (A(J - 1) + (A(J) - A(J - 1)) * ((X - J + 2) / INC)) * RISE
  2. For all others shapes, X = Q / (SPAN * SQR(RISE^3)): SR = SR(IC)
    IH = (A + (B + (C + (D + (E + F * X) * X) * X) * X) * X - SR * S0) * RISE
  3. Headwater elevation (IHI) = IH + I1E if no Depression.
  4. For Depression, CREST headwater is checked.


Throat Control Tapered Inlet

  1. X = Q / (SPAN * SQR(RISE^3))
  2. HT=RISE*(.1295033+(.3789944+(-.0437778+(4.26329E-03-1.06358E-04*X)*X)*X)*X)


Face Control-Side Tapered Inlet

  1. ZZ = Q / (BF * SQR(RISE^3))
  2. Calculate UNSUBMERGED: HF1 = (.56 * RISE) * (ZZ ^ .66667)
  3. Calculate SUBMERGED
    A. For bevels: HF3 = (.0378 * (ZZ * ZZ) + .86) * RISE
    IF HF1 > RISE THEN HF = HF3
    IF HF1 < RISE THEN HF = HF1
    IF HF1 >= HF3 THEN HF = HF1
    B. For other edges: HF2 = (.0446 * (ZZ * ZZ) + .84) * RISE
    IF HF1 > RISE THEN HF = HF2
    IF HF1 < RISE THEN HF = HF1
    IF HF1 >= HF2 THEN HF = HF1


Face Control For Slope Tapered Inlet

  1. ZZ = Q / (BF * SQR(RISE^3))
  2. Calculate UNSUBMERGED: HF1 = (.5 * RISE) * (ZZ ^ .66667)
    A. For bevels: HF3 = (.0378 * (ZZ * ZZ) + .7) * RISE
    IF HF1 > RISE THEN HF = HF3
    IF HF1 < RISE THEN HF = HF1
    IF HF1 > HF3 THEN HF = HF1
    B. For other edges: HF2 = (.0446 * (ZZ * ZZ) + .64) * RISE
    IF HF1 > RISE THEN HF = HF2
    IF HF1 < RISE THEN HF = HF1
    IF HF1 > HF2 THEN HF = HF1


Crest ControlL

  1. HC = .5 * (Q / CW) ^ .66667


Outlet Control Procedures That Produce an Inlet Control Profile

STEP

  1. Compute critical depth (dco)
  2. Compute normal depth (dno)
  3. Compute fullflow if nomograph solution assumed "6-FFt or FFc".
  4. If dno > .95(rise), assume fullflow "6-FFn".
  5. If dno > dco, assume mild slope (SEE OUTLET.DAT).
  6. If dno <= dco, assume steep slope.
    A. If twh is >= So(L) + rise, assume fullflow "4-FFt".\
    B. If twh is >= rise, outlet submerged, assume inlet unsubmerged.
    C. If twh is < rise, outlet is unsubmerged, assume inlet unsubmerged.
    i. Assume headwater (oh) = inlet control headwater (ih)
    Calculate S2 curve "1-S2n" for outlet depth.
    If oh >= rise, inlet submerged "5-S2n"
    ii. If twh > headwater, tailwater drowns out jump.
    Calculate M1 curve "3-M1t".
    If culvert flows part full, "7-Mit".
HY8Inlet Control Chart.jpg


v • e
HY-8
Introduction:Getting Started   •   Layout   •   Vena Contracta   •   Building a Project   •   Locate Project   •   Culvert Crossing Data   •   Run Analysis   •   Report Generation
Crossing and Culvert Data:Crossings   •   Discharge Data   •   Roadway Data   •   Tailwater Data   •   Irregular Channel   •   Culvert Data   •   Site Data   •   Culvert Invert Data   •   Embankment Toe Data
AnalysisProject Units   •   Roadway Overtopping   •   Inlet Control Computations   •   Outlet Control Computations   •   Tables and Plots
Energy DissipationScour Hole Geometry   •   Increased Resistance   •   Tumbling Flow   •   USBR Type IX Baffled Apron   •   Drop Structures   •   Stilling Basins   •   Streambed Level Structures
MethodsAquatic Organism Passage   •   Low Flow Hydraulics
TroubleshootingDifferences from DOS HY-8   •   Limitations   •   HY-8 User Manual
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