N Uday Bhaskar

Bio: N Uday Bhaskar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Caisson. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

Wave forces on a seawater intake caisson

Abstract: The wave force on a seawater intake structure consisting of a perforated square caisson of 400 mm×400 mm size encircling a vertical suction pipe of 160-mm diameter is investigated using physical model studies. The porosity of caisson was varied from 1.6 to 16.9%. Regular and random waves of wide range of heights and periods were used. It is found that the force ratio (ratio of the force on perforated caisson to the force on caisson with zero percent porosity) reduces to an extent of up to 60% with increase in porosity of the caisson from 1.6 to 16.9%. The force ratio was found to increase with increase in relative wave height and reduces with increase in relative width. Multiple regression analysis of the measured data points was carried out and predictive equations for wave force ratios are obtained both for regular and random waves. The results of this investigation can be used in the hydrodynamic design of perforated caissons, which are widely used as seawater intake structures.

Dynamic Analysis and Design of Offshore Structures

Abstract: This chapter deals with the evolution of platform and various types of offshore platforms and their structural action under different environmental loads. The newly evolved structural forms and their discrete characteristics are discussed in this chapter. This chapter also gives the reader a good understanding about the structural action of different forms in the offshore. An overview of the construction stages of offshore plants and their foundation systems is presented.

Uplift capacity prediction of suction caisson in clay using a hybrid intelligence method (GMDH-HS)

Abstract: Suction caissons are widely used for offshore facilities foundation or anchor system. They should be very stable and also to provide stability of main massive structures those are upon them. Suction caisson uplift capacity is the main issue to determine their stability. During recent years, many artificial intelligence (AI) methods such as artificial neural network (ANN), genetic programming (GP) and multivariate adaptive regression spline (MARS) have been used for suction caisson uplift capacity prediction. In this study, a novel hybrid intelligent method based on combination of group method of data handling (GMDH) and harmony search (HS) optimization method which is called GMDH-HS has been developed for suction caisson uplift capacity prediction. At first, the Mackey-Glass time series data were used for validation of developed method. The results of Mackey-Glass modeling were compared to conventional GMDH with two kinds of transfer function called GMDH1 and GMDH2. Five statistical indices such as coefficient of efficiency (CE), root mean square Error (RMSE), mean square relative error (MSRE), mean absolute percentage error (MAPE) and relative bias (RB) were used to evaluate performance of applied method. Then the GMDH-HS method has been used for suction caisson uplift capacity prediction. The 62 data set of laboratory measurements were collected from published literature that 51 sets used to train new developed method and the remaining data set used for testing. Not only the results of suction caisson uplift capacity prediction using GMDH-HS were evaluated with statistical indices, but also the results were compared to some artificial methods by previously works. The results indicated that performance of GMDH-HS was found more efficient when compared to other applied method in predicting the suction caisson uplift capacity.

Hydrodynamics of a Concentric Twin Perforated Circular Cylinder System

Abstract: An experimental investigations was carried out on a perforated circular cylinder ( 0.50 m diameter) encircling an impermeable cylinder ( 0.05 m diameter) at a constant water depth of 0.7 m for both regular and random waves in the wave flume at the Department of Ocean Engineering, Indian Institute of Technology, Madras, India. The porosity of the outer cylinder was varied from 4.54 to 19.15% to study the influence of porosity on wave forces on and water surface fluctuations in and around the twin cylinder system. A numerical method is developed based on the boundary integral equation method along with a porous body boundary condition, where the porosity is modeled using the resistance coefficient f and added mass coefficient Ca for regular waves. The resistance coefficient increases with the increase in porosity and wave heights except for a porosity of 4.54%, whereas the added mass coefficient is almost zero. Porosity in the range of 10–15% can be recommended for the perforated cylinder based on the exper...

Wave force on vertically submerged circular thin plate in shallow water

Abstract: The paper presented is a solution of shallow water wave force, using small amplitude linear wave theory on two-dimensional vertically submerged circular thin plates under three different configurations: (1) a surface-piercing circular thin plate, (2) a submerged circular thin plate, and (3) a bottom-standing circular thin plate. Finally Morison's equation is used for the determination of wave force which is based on the linear wave theory. The plate is submerged in water near the shore on uniformly sloping bottom. The solution method is confined in a finite domain, which contains both the region of different depth of water and the plate. Laplace's equation and boundary value problems are solved in a finite domain, by the method of separation of variables and the small amplitude linear wave theory. The variation of horizontal force by single particle, total horizontal force and moment with respect to the wave amplitude are obtained at different depth of water and at different wave period. It is observed that the force and moment are converging with the increase of wave period and the gradients of force and moment with respect to the wave amplitude are extremely high for lower wave period.

Reduction of non-breaking wave loads on caisson type breakwaters using a modified perforated configuration

Abstract: In this study a new type of partially perforated caisson breakwater is introduced with two shallow chambers split horizontally by an impermeable plate at the mean sea level. A plexiglass laboratory model of the structure was manufactured with different frontface perforation ratios and adjustable chamber breadths, then tested under 2D non-breaking regular and irregular waves. The horizontal wave force and wave moment are evaluated as dimensionless parameters from measured pressure–time series. A control group of tests was also conducted with plain vertical face under identical waves, also the wave loads on a vertical face for the same wave properties were computed using Goda (1985) formulation. Results show that the dimensionless wave forces and dimensionless wave moments can be reduced by a ratio up to 35%–40% under regular and irregular waves and structure performance increases with decreasing wave length. The obtained results are also compared with reference to a fully perforated (Jarlan) caisson using the method given by Tabet-Aoul and Lambert (2003) and a general harmony was seen both for the magnitudes and variation of wave loads with dimensionless chamber breadth ( B / L ).