Browsing by Author "Pathirana, KPP"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Thumbnail Image
    item: Conference-Full-text
    Characteristics of hydraulics jumps over rough horizontal beds
    (2013-11-11) Neluwala, NGPB; Karunanayake, KTS; Sandaruwan, KBGM; Pathirana, KPP
    The available knowledge on the behaviour of Hydraulic jump is only for smooth, horizontal channel beds and very limited studied have been reported in literature on the performance of hydraulic jumps on rough beds. This research attempts to investigate on the characteristics of hydraulic jumps formed on rough, horizontal channel beds under different flow conditions. A series of laboratory experiments were carried out in a rectangular flume which consists of artificially roughened beds formed by placing rectangular wooden strips in specific intervals. The hydraulic parameters such as, initial water depths, sequent water depth, and flow rate were measured for different bed roughness. The analysis of experimental data showed that the rough bed reduces the distance to the jump from the gate and the sequent depth ratio than in those smooth beds while creating a high energy loss. With the availability of large number of experimental data on hydraulic jumps over rough channel beds, theoretical formulations were developed to express the hydraulic jump characteristics relating roughness parameters such as; roughness density and roughness height.
  • Thumbnail Image
    item: Conference-Full-text
    Experimental Investigation of Performance of Reef Breakwaters
    (2016-01-04) Rathnayaka, RMDB; Rathnayaka, RMJR; Pathirana, KPP
    Reef breakwater is a low crested, rubble mound breakwater without a conventional multilayered cross section. It has been identified that transmission coefficient is one of the main parameters to quantify the performance of reef breakwaters and several parameters that influence transmission coefficient was identified. Accordingly, a comprehensive laboratory investigation was carried out and transmission of different reef breakwaters was studied by varying different influence parameters. It was observed that wave steepness, crest width and depth of crest submergence are the most influential parameters on transmission coefficient. Comparison between existing equations to calculate transmission coefficient was done using data from the present study. When using existing equations for the same input parameters, it can be seen that estimated transmission coefficient values differ from each other suggesting that their applicability to a real life problem is questionable. Therefore a new improved formula to estimate transmission coefficient was derived using dimensional analysis incorporating more influence parameters than existing equations. This formulation proved to be better than the previous equations.
  • Thumbnail Image
    item: Conference-Full-text
    Performance of hydraulics jumps over rough beds
    (2013-11-13) Neluwala, NGPB; Karunanayake, KTS; Sandaruwan, KBGM; Pathirana, KPP
    A hydraulic jump phenomenon is one of the most common phenomena in open channels. It is a process of transition of a supercritical flow into a subcritical flow by dissipating a large amount of energy. The available knowledge on the behavior of hydraulic jump is only for smooth, horizontal channel beds and very limited studied have been reported in literature on the performance of hydraulic jumps on rough beds which is the real situation in the field. This research attempts to investigate the characteristics of hydraulic jumps formed on rough, horizontal channel beds under different flow conditions. A series of laboratory experiments were carried out in a rectangular flume which consists of artificially roughened beds formed by placing rectangular wooden strips in specific intervals. The hydraulic jump parameters such as, initial water depth, sequent water depth, and flow rate were measured for different bed roughness by changing the roughness density (width of roughness element / Spacing) 8% to 37.5%. The analysis of experimental data showed that the rough bed reduces the distance to the jump from the gate than in those smooth beds while creating a high energy loss. Existing equations to describe the behavior of hydraulic jump on rough beds were not in agreement with our experimental results as most of them were derived by keeping the roughness density constant therefore a new theoretical equation was developed using dimensional analysis, a better correlation was found among hydraulic jump parameters that include the roughness density to represent bed roughness. where, y1, y2, t, d, Fr are initial depth, sequent depth, height of roughness element, roughness density and Froude number, respectively. It was found that maximum effect of roughness elements occurred at a roughness density of 0.23. The results of this study confirm the effectiveness of rough beds for energy dissipation below hydraulic structures