Browsing by Author "Jena, B. K."

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A description of tidal propagation in Hooghly estuary using numerical and analytical solutions
(Ocean Engineering, 2018) Jena, B. K.; Sivakholundu, K. M.; Rajkumar, J.
A tidal propagation characteristic of Hooghly estuary is presented using numerical (ADCIRC) and analytical models (Friedrichs and Aubrey, 1994) along with observations. The analytical model is based on Friedrichs and Aubrey (1994) that simplifies the governing hydrodynamic equations greatly by retaining only those terms that are significant without losing the overall understanding of the propagation process. The analytical model is compared with corresponding 2-D depth averaged numerical (ADCIRC) model that retains all non-linear terms. The assumptions for simplification are found to be reasonable in the light of close agreement among analytical, numerical models and observations. A plan-form geometrical characteristic as well as hydrodynamic variable of the Hooghly has been compared with that of Delaware estuary for corroborating similar tidal propagation process. The Hooghly estuary has flood dominant asymmetric tidal propagation and a positive amplitude growth factor (μ). The observed tidal celerity (phase speed) on an average is slightly more than frictionless celerity. Using the conventions of Toffolon et al. (2006), Hooghly can be classified into ‘strongly convergent – strongly dissipative’ estuary. From the results it can be construed that the estuary is yet to stabilise and reach its equilibrium morphology. It can be close to its equilibrium as very little amplification (0.1 m) is noticed in the predominant semi-diurnal constituent M2 over 78 km (barely 7%) in the estuary. The parameters of width variation (γ) and the ratio between friction and inertia (χ) have been used to define the marginal condition for amplification. The relative position of Hooghly in terms of marginal condition is consistent with similar set of estuaries elsewhere that have been grouped using the above parameters.
Long term port monitoring system (PMS)
(Indian Journal of Geo-Marine Sciences, 2014) Suseentharan, V.; Sivakholundu, K. M.; Jena, B. K. ; Ravinder, M.; Balaji, Rajoo
NIOT has developed and operated a Port Monitoring System (PMS) at Gujarat Pipavav Port Limited (GPPL) to measure tide and current on real time. PMS consists of a pressure based tide gauge and a Horizontal Acoustic Doppler Current Profiler (H-ADCP) installed at 5 m depth w.r.t Chart Datum (CD). Tide, current speed and direction are measured and transmitted to NIOT server in real time and data is presented through web application after quality check (QC). The success and high utility of the data at GPPL has resulted in requests for similar installations in other ports (Mundra, Dahej, Hazira, Vizhinjam, Dhamra and IGCAR) which enabled NIOT to expand the PMS network. The system can be used with different communication links like GPRS, UHF and INSAT. Using GPRS link, the sensors can be configured remotely to change the sampling regime and communication interval. Being a modular design, the PMS has an option for integrating more sensors for met-ocean and water quality parameters depending on site or study specific requirement. The paper discusses the basic architecture, options that can be built and the experience gained during development, installation and operation in various site conditions.
Seasonal and interannual changes of significant wave height in shelf seas around India during 1998–2012 based on wave hindcast
(Ocean Engineering, 2018) Sanil Kumar, V.; Dubhashi, K. K.; Amrutha, M. M.; Joseph, Jossia; Jena, B. K. ; Sivakholundu, K. M.
Present study examines the interannual changes of significant wave height (Hs) in shelf seas around Indian mainland based on the 15-year (1998–2012) wave hindcast data obtained from numerical model. Validation of the hindcast data with buoy-measured data shows that hindcast Hs is reasonably in good agreement with the observation (Pearson correlation coefficient values of 0.92–0.97). Annual average Hs varied from 0.9 to 1.4 m and the wave heights are higher (∼20%) in western shelf seas compared to eastern shelf seas. The analysis reveals seasonal fluctuations of wave climate, with a strong influence of Asian summer monsoon in the western shelf seas compared to the eastern shelf seas of India. Maximum Hs varied from 3.65 to 7.36 m and these maximum values were during the tropical cyclones. During 1998 to 2012, a statistically significant positive trend of 0.8–1.4 cm yr−1 in annual mean Hs is observed and the increasing trend is higher (∼0.7–2.5 cm yr−1) during the Asian summer monsoon period (June–September). The average trend of annual mean wind speed is also positive and is higher (∼1.67 cm s−1 yr−1) for the western shelf seas than that for eastern shelf seas (∼0.93 cm s−1 yr−1).
Seasonal variation in nearshore wave characteristics offCuddalore, Southeast coast of Tamil Nadu, India
(Current Science, 2017-05) Jena, B. K.; Patra, Sisir K.; Joseph, K. Jossica; Sivakholundu, K. M.
Wave data collected using wave rider buoy between January 2010 and January 2011 off Cuddalore coast, Tamil Nadu, India, have been analysed season-wise in this study. Wave steepness method was used for the separation of sea and swell wave parameters. Also parameters such as significant wave height of total wave, sea and swell (Hs , Hsw and Hss), zero crossing periods (Tz, Tsw and Tss) and mean wave directions (,sw and ss) have been studied. The study shows a distinct shift in sea wave direction of about 90 between June and October as well as November and February. Throughout the year, the predominant swell direction remained around 135. The contribution in total Hs by Hsw was 76% and the remaining 24% by Hss in the yearly cycle. The sea wave height was dominant by more than 90% during November to May. Regression analysis showed good positive Pearson’s correlation of 0.94 between Hs and Hsw; however, it was 0.65 between Hs and Hss. The maximum and significant wave heights of 5.7 and 2.7 m were recorded during cyclone Jal on 7 November 2010.
Surface current and wave measurement during cyclone Phailin by high frequency radars along the Indian coast
(Current Science, 2015-02) John, Manu; Jena, B. K.; Sivakholundu, K. M.
Cyclone Phailin originated in the east central Bay of Bengal (BoB) and crossed into the Indian mainland after traversing through the BoB. High frequency radar (HFR) operated by the National Institute of Ocean Technology could track the surface currents and high wave activity within its measuring limits. The radar data provide valuable information on the surface dynamics during the cyclone period. The HFR observations compare well with those of wave rider buoy. This opens up opportunities for observing the wave conditions during the cyclonic period over longer distances from the shore. This method is relatively more robust as HFR is less likely to be disrupted due to the passage of cyclones, unlike moored systems.