Experimental Study of Local Scour around Tripod Foundation in Combined Collinear Waves-Current Conditions

A series of laboratory experiments were conducted in a wave-current flume to investigate the scour evolution and scour morphology around tripod in combined waves and current. The tripod model was made using the 3D printing technology, and it was installed in seabed with three installation angles α = 0°, 90°and 180° respectively. In the present study, the scour evolution and scour characteristic were first analyzed. Then, the equilibrium scour depth Seq was investigated. Furthermore, a parametric study was carried out to study the effects of Froude number Fr and Euler number Eu on equilibrium scour depth Seq respectively. Finally, the effects of tripod’s structural elements on Seq were discussed. The results indicate that the maximum scour hole appeared underneath the main column for installation angle α = 0°, 90° and 180°. The Seq for α = 90° was greater than the case of α = 0° and α = 180°, implying the tripod suffered from more severe scour for α = 90°. When KC was fixed, the dimensionless time scale T* for α = 90° was slightly larger than the case of α = 0° and α = 180° and the T* was linearly correlated with Ucw in the range of 0.347 < Ucw < 0.739. The higher Fr and Eu both resulted in the greater scour depth for tripod in combined waves and current. The logarithmic formula can depict the general trend of Seq and Fr (Eu) for tripod in combined waves and current.

Comparison of shortcut methods for designing of divided wall columns for separating tertiary zeotropic mixtures

Recently, divided wall column has been considered as one of the types of thermally coupled towers for separating multicomponent mixtures. In the structure of this tower, there is a wall that divides the tower into two parts, the Prefractionator and the Main Column. The divided wall column is thermodynamically equivalent of the Petlyuk tower. Therefore, in order to obtain the design and simulation parameters of the Petlyuk tower utilizing the available software, this tower must be divided into simpler towers. The shortcut method is employed to acquire the initial parameters. In the present research, initially, the design of divided wall column has been conducted using shortcut methods to separate three-component zeotropic mixtures. Next, the design and simulation of the divided wall column is performed employing ASPEN PLUS software and the results of the two methods are compared from various angles.

Analisa Perbandingan Kolom Komposit Inside Steel dan Outside Steel terhadap Kapasitas Tahanan Aksial dan Momen

ABSTRAK Penggunaan kolom komposit telah banyak digunakan di berbagai bangunan bangunan tinggi. Dan pada umumnya, Kolom komposit dibagi menjadi 2 macam, yaitu kolom komposit inside steel dan outside steel dengan struktur baja terbungkus oleh beton disebut dengan kolom inside steel atau bisa saja disebut Concrete Encased Column. Sedangkan untuk baja yang berisi beton disebut dengan kolom outside steel atau juga disebut Concrete Filled Column. Penggunaan struktur kolom komposit outside steel sebagai kolom utama dalam mendukung beban lateral pada struktur rangka bangunan belum lazim digunakan dalam perkembangan konstruksi saat ini. Oleh karena itu, perlu dilakukan analisa kekuatan dari 2 macam kolom komposit agar diketahui jenis kolom komposit yang paling efektif dan memiliki kekuatan paling tinggi. Perhitungan yang dilakukan dengan menggunakan perhitungan manual pada kolom komposit inside steel dan outside steel yang berbentuk kotak, sedangkan untuk perhitungan dengan menggunakan program CSICOL dilakukan pada seluruh kolom komposit. Hasil nilai ØPn dan ØMn kemudian dibandingkan antara perhitungan manual dengan program CSICOL. Hasil perhitungan menunjukan bahwa kemampuan kolom komposit outside steel lebih baik dibandingkan kolom komposit inside steel dengan menggunakan standar volume dari ukuran kolom komposit inside steel kotak 400x400 mm. Kolom komposit outside steel berbentuk bundar dengan diameter 431 mm lebih unggul sebesar 17 % dalam menahan gaya aksial nominal (ØPn) dibandingkan semua tipe kolom komposit yang lain. Sedangkan kolom komposit outside steel berbentuk kotak dengan ukuran 405.70x405.70 mm lebih unggul menahan momen nominal (ØMn) sebesar 10,5 % dibandingkan semua tipe kolom komposit yang lain.Kata kunci : kolom komposit; inside steel (concrete- encased column); outside steel (concrete-filled column)ABSTRACT The use of composite columns has been widely used in various high-rise buildings. Composite columns are generally divided into two types: composite columns inside steel and outside steel columns with a steel structure wrapped in concrete called an inside steel column (concrete encased column), while steel containing concrete is called an outside steel column (concrete-filled column). The use of a composite column structure outside steel as the main column in supporting lateral loads in the building frame structure is not yet commonly used in current construction developments. Therefore, it is necessary to consider the strengths of 2 types of composite columns to know which type of composite column is the most effective and has the highest strength. Calculations are performed using manual calculations on composite columns inside steel and outside steel in the form of a box, while calculations using the CSiCOL program are carried out on all composite columns. The results of the ØPn and ØMn values are then compared between manual calculations and the CSiCOL program. The calculation results show that the composite outside steel column's ability is better than the inside steel composite column by using a standard volume from the size of the composite column inside steel box 400x400 mm. The round composite outside steel column with a 431 mm diameter is 17% superior in withstanding nominal axial force (ØPn) than all other composite column types. While the outside steel composite column in the form of a box with a size of 405.70x405.70 mm is superior to withstand the little moment (ØMn) by 10.5% compared to all other types of composite columns.

Penilaian Risiko, Estimasi Interval Inspeksi, dan Metode Inspeksi pada Hydrocarbon Piping Menggunakan Metode Risk Based Inspection (RBI)

Piping adalah sistem perpipaan yang digunakan untuk mengalirkan fluida dari satu proses ke proses lainnya. Jenis piping yang diteliti adalah Hydrocarbon Piping yaitu sebagai penyalur fluida antara reaktor, regenerator, dan main column pada proses catalytic cracking. Fluida yang mengalir pada Hydrocarbon Piping dapat menyebabkan korosi dan mengakibatkan terjadinya penipisan bahkan kebocoran pipa sehingga menimbulkan dampak yang buruk, baik pada lingkungan, keamanan, keselamatan, dan kerugian biaya. Peralatan bertekanan seperti piping memerlukan program inspeksi agar dapat bekerja dengan baik. Risk Based Inspection (RBI) adalah suatu metode untuk menentukan rencana program inspeksi berdasarkan risiko kegagalan peralatan. Metode RBI yang digunakan adalah RBI Semi-Kuantitatif dengan standar API 581. Tujuan penelitian ini adalah untuk mengetahui tingkatan risiko, estimasi interval inspeksi, dan penentuan metode inspeksi pada piping. Dari hasil penelitian menunjukkan bahwa Hydrocarbon Piping terdiri dari 16% pipa dengan tingkat risiko low dan 84% pipa dengan tingkat risiko medium. Estimasi interval inspeksi dianjurkan tidak melebihi setengah remaining life pipa. Dengan mekanisme kerusakan thinning, metode inspeksi yang dianjurkan ialah profile radiography, UT scans, dan visual examination.

IMPROVEMENT OF THE CONSTRUCTION AND COMPUTER DEVICE INVESTIGATION FOR THE PROCESSING OF BLOWOUT-PREVENTION HARDWARE EQUIPMENT

The research deals with the problem of blowout equipment test for tightness before implementation. The indicated equipment includes a stem, a system of pipelines with valves and a control system. The classic test procedure requires a mobile pumping installation that provides a pressure of 35 MPa.The cost of such tests is rather high. For testing without a pump unit, a design of a device for increased tightness has been developed, including a sealing unit of the mouth from the main column and a piston unit for creating high pressure in the test volume. Generation of a high pressure occurs by lifting the piston with a winch, mounted on the well. Disadvantages of the previously proposed design of the device are as follows. There is a considerable friction between the steel moving parts of the sealing unit. Mostly these are the pairs of a plug and a cup, and a chuck and a cone. Tightness is provided by rubber ring sleeves. Exceedence of axial load on cones causes destruction of sealing rings. The authors of the article improved the design of the sealing unit in the following way: a ball thrust bearing was seated between the ends of the pressure plug and the bottom cup and as a result the sliding friction was replaced with sliding friction. On the outer surfaces of the opening cones in contact with clamping blades, it is proposed to paste a tissue antifriction material of type Nafthlene or equivalent. The friction coefficient in such pairs is next lower order than in steel to steel pairs. The computer model of the device has been created in the Solid Works environment. The computer researches of the loading process of components of the sealing unit in the simulation program based on the finite element method were performed. As a result of the research, recommended values ​​of the axial force, required to create a screw pair of a stem and a plug for sufficient radial axial deformation of elastic cuffs with the simultaneous non-admission of their destruction were identified. Also, the design dimensions of the pressure cups of the device were optimized, namely, the mutual axial placement of the end face, which presses on the cone, and the tapered belt, compressing the sealing ring. The determination of these parameters by an experiment is a long and expensive process.

A Novel Semi-Submersible Floating Wind Turbine Platform Design Based on Tuned Liquid Column Dampers

Floating offshore wind turbine (FOWT) has been a hot research topic in recent years due to its great potential in deep sea wind energy harvesting. However, the floating platforms will introduce additional degrees of freedom to the system, which results in much more ultimate and fatigue loads onto the wind turbine structure compared with fixed bottom types. The load issue has been the major design challenge in developing FOWTs. In this paper, we report a novel semi-submersible supporting platform design, named MUsupport, aiming to improve the dynamic responses and reduce loads for FOWTs. The proposed semi-submersible MUsupport is mainly composed of one main column attached to the tower and four offset columns. Particularly, instead of simply filled with ballast water, the four columns act as four tuned liquid column dampers (TLCDs), and the oscillating liquid inside the TLCDs is supposed to help improve the dynamic responses of the semi-submersible platform, thus reducing the loads. The sizing of these TLCDs are determined by frequency analysis, and the detailed structural properties for MUsupport are described in this paper. Additionally, in order to better study the damping effects of the TLCDs, the dynamic model of MUsupport FOWT in the pitch-surge-heave plane is derived based on the Lagrangian approach, and free decay simulation test is performed. It can be observed from the results that the introduction of TLCDs will bring more damping to the system dynamics, which is helpful for FOWT load reduction. Note that this is only preliminary study, and future works will comprehensively investigate its hydrodynamic and mooring behaviors of MUsupport, and aero-hydro-servo-elastic numerical simulations or experimental tests should be performed to further verify its effectiveness.

Atmospheric processes affecting the separation of volcanic ash and SO₂ in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

The separation of volcanic ash and sulfur dioxide (SO2) gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21–28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources coupled with meteorological wind data and photographic evidence suggest that the eruption column was unable to sustain itself, resulting in a large deposition of ash, which left a low-level ash-rich atmospheric plume moving southwards and then eastwards towards the southern Scandinavian coast and a high-level predominantly SO2 plume travelling northwards and then spreading eastwards and westwards. Here we provide observational and modelling perspectives on the separation of ash and SO2 and present quantitative estimates of the masses of ash and SO2 that erupted, the directions of transport, and the likely impacts. We hypothesise that a partial column collapse or sloughing fed with ash from pyroclastic density currents (PDCs) occurred during the early stage of the eruption, leading to an ash-laden gravity intrusion that was swept southwards, separated from the main column. Our model suggests that water-mediated aggregation caused enhanced ash removal because of the plentiful supply of source water from melted glacial ice and from entrained atmospheric water. The analysis also suggests that ash and SO2 should be treated with separate source terms, leading to improvements in forecasting the movement of both types of emissions.

Pembe. The Empire Blanched in Fear, Anger and Shame

On 25 September 1904, a military column that had been deployed to occupy the Kwanyama region in southern Angola was attacked and severely defeated by the Kwamatos. Over two hundred Portuguese soldiers are thought to have died in the fight, of which 109 were Europeans and 145 were Africans. The column left Lubango on 22 August and reached the Humbe, the furthest reach of Portuguese influence in the region, on 11 September. The going was slow because of the rugged terrain and the sluggish Boer cars, and the lack of water made the march toilsome, but it was nonetheless conducted in an organized manner, and there were no major incidents. On 19 September, the column, which had meanwhile been reinforced with indigenous companies and auxiliaries, was put in motion, and after 2Kms the troops began crossing the Cunene River. The crossing took a day and a half, with the troops already under Kwamato fire. The Battle of the Ford of Pembe had begun. The forces commanded by Captain João Maria Aguiar, Governor of Huila Province, bivouacked in square once they reached the left bank of the river. The bulk of the troops remained stationed there for six days, during which they were buffeted with constant lowintensity attacks. On the 23rd, an offensive reconnaissance action commanded by then Captain Gomes da Costa came into direct confrontation with the Kwamatos, who did not put up significant resistance. The troops took advantage of the opportunity to set fire to a few libatas [dwellings] and to carry out a more thorough reconnaissance of the surrounding territory. Two days later, a new detachment entered the woods, this time commanded by Captain Pinto de Almeida and, approximately 8Kms from the main column, in the Umpungo chana2, it was surrounded by Kwamato forces and completely destroyed. A few retreating soldiers were even hit by friendly fire from the artillery stationed along the river. That same day, the survivors retreated toward Humbe, crossing the Cunene in only three hours, leaving behind provisions, wine barrels, wire, all the zinc sheets they had used to protect the trenches, which had been built to protect the square, and many heavy supplies. A thunderstorm had meanwhile broken below the plateau, hindering telegraphic communications. Still, the first news of this upsetting event reached Moçâmedes as early as the 28th. Uncertainty and incredulity abounded during those first few days, but feelings of consternation and revolt soon began to spread. In Portugal, it was not until October that the initial reports were disclosed to great commotion. Displays of grief and religious ceremonies in honour of the dead multiplied across the country, while heated discussions erupted in the two houses of parliament, led by representatives of the Progressive Party, the opposition party at the time. At the same time, there were calls for punitive expeditions, and several disciplinary inquiries were launched which culminated with the appearance of the commander of the expedition before the War Council. The thinking produced by military circles, which sought to find an explanation for the events, often opened up new advanced platforms of analysis for the organics of the military mechanisms overseas.

Videofluoroscopic examination – study procedure with an assessment questionnaire

In this article, we proposed a questionnaire for assessment of videofluorscopic examination in patients with swallowing disorders. It was developed during years 2015 - 2016 by the Department of Otolaryngology at the Medical University of Warsaw. The main body of the form consists of 3 parts assessing the oral phase, the pharyngeal phase and the esophageal phase. The main column contains a list of specific symptoms with yes/no answers. There is a four-point scale assessing the severity of the disorders from 0 to 3, where 0 corresponds to clinically insignificant findings, 1- mild impairment, 2 - moderate impairment, and 3 – severe impairment. Other elements of the form include: basic demographic and nutritional data, assessment of the consistency and texture of ingested food, food texture recommended based on the evaluation acc. to the recommendations of the International Dysphagia Diet Standardization Initiative (www.iddsi.org), and therapeutic assessment before implementation of speech therapy. The questionnaire was prepared on the basis of Trinity College survey, own experience and literature data.