Three-Dimensional Numerical
Simulation of Pressure-Flow Scour
Sofi Aamir Majid and Shivam Tripathi
Abstract An estimate of scour depth is required in the design of bridges. Much of
the research on scour estimation has focussed on the local scouring, i.e. scouring
near abutments or around piers. In comparison, contraction scouring has received
less attention. Contraction scouring occurs when the waterway is contracted either
laterally or vertically. During extreme flood events, the water level may rise above the
bottom chord of the bridge, creating a pressure-flow situation in the passage below
the bridge. The pressure scour thus induced is not clearly understood in terms of its
location, geometry and time evolution. Some recent experimental studies have tried
to establish empirical relations between scour parameters and various properties of
flow, fluid and bed material. However, numerical approach has not been employed
to study the pressure scour. The present study is an attempt to numerically simulate
the pressure scour caused due to vertical contraction. International River Interface
Cooperative (iRIC) solver NAYSCube is used to simulate the flow over mobile bed.
NAYSCube, an open source 3D flow solver, employs finite volume method to solve
Navier–Stokes equations and couples turbulence and bed-load models. Due to the
limitations of the computational capacity, the simulations are performed to generate
the flow and bed data for a period of one hour. The approaching flow velocity,
channel slope and the sediment size of the bed are kept constant. The results show
that bed shear has the maximum value inside the contraction section. The scour
hole is observed to develop within the contraction towards the upstream face of the
contraction. The magnitude of maximum scour is found to increase with increase in
degree of contraction or length of contraction or both. The study establishes the need
to conduct more numerical simulations to investigate pressure-flow scouring.
Keywords Bed scour · Pressure flow · Sediment transport · Numerical simulation
S. A. Majid (B) · S. Tripathi
Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
e-mail: aamirm@iitk.ac.in
© Springer Nature Singapore Pte Ltd. 2021
C. Bhuiyan et al. (eds.), Water Security and Sustainability,
Lecture Notes in Civil Engineering 115,
https://doi.org/10.1007/978-981-15-9805-0_2
11
Simulation of Pressure-Flow Scour
Sofi Aamir Majid and Shivam Tripathi
Abstract An estimate of scour depth is required in the design of bridges. Much of
the research on scour estimation has focussed on the local scouring, i.e. scouring
near abutments or around piers. In comparison, contraction scouring has received
less attention. Contraction scouring occurs when the waterway is contracted either
laterally or vertically. During extreme flood events, the water level may rise above the
bottom chord of the bridge, creating a pressure-flow situation in the passage below
the bridge. The pressure scour thus induced is not clearly understood in terms of its
location, geometry and time evolution. Some recent experimental studies have tried
to establish empirical relations between scour parameters and various properties of
flow, fluid and bed material. However, numerical approach has not been employed
to study the pressure scour. The present study is an attempt to numerically simulate
the pressure scour caused due to vertical contraction. International River Interface
Cooperative (iRIC) solver NAYSCube is used to simulate the flow over mobile bed.
NAYSCube, an open source 3D flow solver, employs finite volume method to solve
Navier–Stokes equations and couples turbulence and bed-load models. Due to the
limitations of the computational capacity, the simulations are performed to generate
the flow and bed data for a period of one hour. The approaching flow velocity,
channel slope and the sediment size of the bed are kept constant. The results show
that bed shear has the maximum value inside the contraction section. The scour
hole is observed to develop within the contraction towards the upstream face of the
contraction. The magnitude of maximum scour is found to increase with increase in
degree of contraction or length of contraction or both. The study establishes the need
to conduct more numerical simulations to investigate pressure-flow scouring.
Keywords Bed scour · Pressure flow · Sediment transport · Numerical simulation
S. A. Majid (B) · S. Tripathi
Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
e-mail: aamirm@iitk.ac.in
© Springer Nature Singapore Pte Ltd. 2021
C. Bhuiyan et al. (eds.), Water Security and Sustainability,
Lecture Notes in Civil Engineering 115,
https://doi.org/10.1007/978-981-15-9805-0_2
11