Electrical energy shortage and expensive basic electricity costs are one of the problems that are occurred in Karimunjawa Island, Indonesia. The purpose of this research is to identify the potential of ocean currents energy as one of the alternatives to reduce the problem related to energy needs and to predict the electrical energy that can be obtained. The physical phenomena movement of ocean currents is made by using the 2-Dimensional hydrodynamic mathematical model. ADCP Multicell Argonaut-XR type is used to measure the speed of ocean currents to validate the model result. Tidal, wind, coordinate and bathymetry data are all the variables that are in the mathematical model of ocean current movement. The potential of electrical energy is determined by the value of power density which is calculated based on the speed ocean current model. The result of this research is the map of the potential distribution of ocean currents in Karimunjawa waters.
The previous studies have simulated the variability of the wave within the Indonesian seas which showed that the variability of wave follows the seasonal pattern. However, their analysis only consider the influence of local wind forcings. The bias and error of their simulated wave were also unclear. In the present study, we investigate the variability of wave within the Indonesian seas and its relation with the surface wind speed using the combination of reanalysis and remote sensing data with high accuracies. We split the analysis into swell and wind wave to obtain the influence of local and remote wind forcings. We show that at the inner seas (i.e., the South China Sea, Java Sea, Flores Sea, Banda Sea and Arafura Sea), the variability of significant wave height (SWH) is majorly influenced by the variability of the speed of monsoon wind. The maximum SWH during Northwest monsoon (NWM) season is located at the South China Sea while during Southeast monsoon (SEM) season is at Arafura Sea. This indicates that the wind wave (sea) is dominant at the inner seas. At the open seas (i.e., Pacific Ocean and Indian Ocean) the variability of SWH less corresponds to the the speed of monsoon wind. The remote wind forcings control the wave variability in the open ocean area. This indicates that swell is dominant at the open seas. In general, the magnitude of SWHswell is also more than SWHsea within the Indonesian seas.
Massive mangrove conversion into intensive pond farming has become environmental problem in Kemujan Island and Karimunjawa Island which affect the water quality. This research aimed to examine the dispersion of DO and BOD related to the current pattern in the seas west of Kemujan Island and Karimunjawa Island by using two-dimensional modelling simulations. Quantitative and descriptive methods were used to provide interpretation and analysis of the modelling simulation results. Modelling simulations were conducted in September 2019. The validation results show that the model and the field measurements has a very good. The results show that the current characteristics are dominated by tidal current, which moves westward with an average magnitude of 0.078 m/s. Furthermore, divergence, convergence and turbulence are also identified. Based on the simulation results, the prediction of DO and BOD concentrations fluctuate in Lagoon Mrican. During spring tide, the DO concentration changes from 7.95 - 8.1 mg/L into 8.55 - >9.45 mg/L and during neap tide, it changes from 8.55 - 8.7 mg/L into 9.15 - >9.45 mg/L. On the other hand, the BOD concentration increases from 0 - 0.08 mg/L to 0.88 - 0.96 mg/L during spring tide and neap tide.
Pelabuhan Malahayati menjadi alur lintas serta tempat sandar bagi peti kemas domestik. Untuk menjalankan aktifitas pelabuhan secara optimal serta merencanakan pembangunan pelabuhan, pengetahuan mengenai tipe dan karakteristik pasang surut sangat penting. Pengolahan data pasang surut dengan berbagai metode dapat memberikan hasil yang berbeda-beda. Tujuan penelitian ini adalah untuk mengetahui karakteristik pasang surut dan komponen harmonik pembangkit pada lokasi penelitian, mengetahui perbandingan hasil pengolahan pasang surut dengan metode admiralty, least square dan fast fourier transform. Serta melakukan prediksi elevasi pasang surut dengan metode least square pada waktu setelah penelitian. Validasi hasil pengolahan pasang surut dilakukan dengan menghitung nilai RMSE hasil pengolahan metode least square terhadap data lapangan. Ketiga metode menghasilkan tipe pasang surut Pelabuhan Malahayati yaitu tipe pasang surut harian ganda. Metode admiralty menghasilkan 9 komponen utama pasang surut, sedangkan metode least square menhasilkan sejumlah 68 komponen. Sementara metode FFT digunakan untuk mengidentifikasi 21 komponen harmonik pasang surut Pelabuhan Malahayati. Didapatkan dominasi komponen harmonik pasang surut pada Pelabuhan Malahayati, yaitu komponen semidiurnal (M2 dan S2). Didapatkan nilai RMSE pada hasil pengolahan sebesar 32 cm, sedangkan RMSE hasil prediksi sebesar 64 cm. Perbedaan nilai formzhal kurang dari 0.02 sedangkan perbedaan nilai amplitudo masing-masing komponen pasang surut kurang dari 0.1 meter. Malahayati Port serves as crossing lane and transit for domestic container ships. To carry out port activities optimally and design port development, knowledge of the types and characteristics of the tides in the location is very important. This study was to determine the tidal characteristics and harmonic components of the Malahayati Port, to compare the results of tidal processing using 3 methods (admiralty, least square and fast fourier transform) and to predict the elevation of tides after this study using the least square method. Validation on this study was done by calculating the RMSE between least square result and field data. All of the 3 methods resulted the Malahayati Port tidal type which was semi diurnal tide. The admiralty method produced 9 major components, while the least square produced 68 of tidal harmonic components. And the FFT is used to identify 21 harmonic components of the Malahayati Port. Obtained that the dominance of the tidal harmonic component at the Malahayati Port was semidiurnal component M2 and S2. Noted that the RMSE value between least square result and field data is 32 cm, while the prediction RMSE is 64 cm. Using 3 methods the Formzhal difference is less than 0.02 while the difference in the amplitude of tidal component is less than 0.1 meters.
Lokasi geografis Teluk Lampung yang terletak di Pulau Sumatra bagian Selatan dan dipisahkan dari Pulau Jawa melalui Selat Sunda mempunyai akses langsung dengan perairan lepas dari Samudera Hindia. Hal ini akan berpengaruh terhadap pola sirkulasi arus permukaan yang terbentuk. Penelitian ini bertujuan untuk memodelkan arus permukaan di Teluk Lampung dengan menggunakan pendekatan model hidrodinamika khususnya pada musim peralihan II (Oktober – November 2020). Verifikasi model dilakukan dengan cara membandingkan hasil model arus dengan hasil pengukuran arus lapangan menggunakan currentmeter valeport yang dilaksanakan dari tanggal 12 Oktober sampai 9 November 2020. Hasil penelitian menunjukkan bahwa arus permukaan dominan dibangkitkan oleh pasang surut dengan prosentase arus pasang surut sebesar 89,09 %. Tipe pasang surut adalah tipe campuran condong harian ganda dengan nilai Formzahl 0,4. Kecepatan arus maksimum 0,168 m/s ke arah 352° dan arus minimum 0,017 ke arah 33°, sehingga arah pergerakan cenderung bolak balik. Pada kondisi pasang, arus bergerak ke utara yaitu dari Selat Sunda masuk ke perairan Teluk Lampung, dan sebaliknya pada saat surut arus bergerak ke arah selatan keluar dari perairan Teluk Lampung menuju Selat Sunda. The geographical location of Lampung Bay, which is located in the southern part of Sumatra Island and separated from Java Island by the Sunda Strait, has direct access to the waters off the Indian Ocean. This will affect the surface current circulation pattern that is formed. This research aims to model surface currents in Lampung Bay using a hydrodynamic model approach, especially in 2nd transitional monsoon (October - November 2020). Model verification is carried out by comparing the results of the current model with the results of field current measurements using a valeport current meter which was carried out from 12 October to 9 November 2020. The results showed that the dominant surface current was generated by tides with a tidal current percentage of 89.09%. The tidal type is a mixed type of mixed tide prevailing semidiurnal with a Formzahl value of 0.4. The maximum current speed is 0.168 m/s in the direction of 352° and the minimum current is 0.017 in the direction of 33°, so that the direction of movement tends to be back and forth. At high tide, the current moves northward from the Sunda Strait into the waters of Lampung Bay, and vice versa at low tide the current moves southward out of the waters of the Lampung Bay towards the Sunda Strait.
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