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Sani, Reza Maulana - One of the best experts on this subject based on the ideXlab platform.

  • Studi Eksperimen Karakteristik Aliran Melintasi Silinder Sirkular Berpengganggu Prisma Segitiga, Prisma Segiempat Dan Silinder Sirkular “Studi Kasus Variasi Jarak Longitudinal (S/D) = 1,45 - 1,70”
    2016
    Co-Authors: Sani, Reza Maulana
    Abstract:

    Aliran yang melewati silinder sirkular sangat banyak dijumpai di dunia teknik seperti pada struktur bangunan pantai, struktur banguan off-shore, bangunan gedung, struktur jembatan dan sebagainya. Gaya seret (drag force) merupakan salah satu gaya akibat adanya aliran yang melewati suatu body. Besarnya gaya drag sebanding dengan daerah wake yang terjadi, artinya semakin kecil wake dibelakang silinder utama maka gaya drag yang terjadi akan semakin kecil. Adanya gaya drag umumnya tidak diinginkan karena dapat mengurangi efisiensi energi. Penelitian ini dilakukan secara eksperimen pada sebuah wind tunnel jenis subsonic dengan benda uji berupa seilinder sirkular dengan diameter 60 mm dan body pengganggu berbentuk prisma segitiga, prisma segiempat, dan silinder sirkular dengan variasi jarak S/D = 1.45; 1.50; 1.55; 1.60; 1.65 dan 1.70; pengujian ini mengunakan bilangan Reynolds = 5,3 x 104 berdasarkan kecepatan free stream dan diameter silinder sirkular. Karakteristik aliran berupa grafik Cp, u/Umax , St dan CD diperoleh dengan mengukur distribusi tekanan pada kontur silinder utama, profil kecepatan dibelakang silinder, frekuensi Vortex shedding dan menghitung gaya drag total. Hasil yang didapatkan dari penelitian ini menunjukkan pengganggu yang paling efektif mengurangi gaya drag ditinjau dari CDp adalah pengganggu tipe D yang mampu mereduksi gaya drag sebesar 79,04% pada jarak S/D = 1,45. Ditinjau dari St/St0, maka pengganggu pengganggu tipe C paling efektif mereduksi gaya drag dengan St/St0 = 1.006 pada jarak S/D = 1.70. Hal ini disebabkan penambahan pengganggu mempercepat transisi lapis batas boundary layer silinder sirkular sehingga mempercepat transisi boundary layer aliran dari laminar menjadi turbulen. Turbulen boundary layer ini lebih efektif menahan adverse pressure serta gaya gesek yang terjadi kemudian mengakibatkan titik separasi mundur ke belakang dan daerah wake menyempit dan menurunkan drag force ============================================================================================= Flow around a circular cylinder has been subjected to extensive research efforts in a wide range of engineering disciplines. Different studies show that this flow configuration has many engineering applications and still presents one of the major challenges in fluid mechanics; for example, bridge piles, Tubes in heat exchangers, and supporting columns for offshore constructions. Therefore, it is still important to continue the study with circular cylinder as an object, especially on a group configuration. In order to reduce the drag coefficient of circular cylinder, some of methods were studied. This study is to present the reducing of aerodynamics forces on a circular cylinder by upstream installation of some bluff bodies as passive control or disturbance, such as square prism, square prism rotate 45o , triangle prism rotate 30o, triangle prism rotate 210o, and cylinder circular. In order to reduce the drag force on a circular cylinder (D = 60 mm), five bluff body; type A, B, C, D, and E having a diameter d or long side of 7,5 mm were used as a passive control. The passive control were located in various spacing positions of S/D = 1.45, 1.50, 1.55, 1.60, 1.65 and 1.70. The experiments were carried out in a subsonic open circuit wind tunnel. This facility has a 1780 mm long, with test section 660 mm x 660 mm. The free stream velocity of wind tunnel could be adjusted constant to 13.6 m/s, corresponding to Reynolds number Re = 5,3 x 104 (based on diameter D and the free stream velocity). Seventy-two pressure taps with interval 5◦ were installed on the wall of the circular cylinder and connected to an inclined kerosene manometer, which it makes it possible to measure the pressure distribution around the circular cylinder. The velocity profile behind the circular cylinder was measured using a pitotstatic Tube connected to the inclined manometer. The Pitot-Static Tube was placed at 18 cm at the rear of the axis of the cylinder or corresponding to x/d = 3, and finally frequency of vortex shedding behind the cylinder was measured at x/D = 3 and y/D = 1 by hot wire anemometer. The experimental result show that there is reduction of drag coefficient on main cylinder by upstream installation of the some bluff body as passive control or cylinder disturbance. The passive control “type D” at S/D = 1.45 gives has the highest drag reduction on the large circular cylinder situated downstream. It gives about 0.21 times the drag of a single cylinde

Johansen, Tor Arne - One of the best experts on this subject based on the ideXlab platform.

  • Globally exponentially stable wind estimation for small fixed-wing UAVs using standard sensors
    'American Institute of Aeronautics and Astronautics (AIAA)', 2020
    Co-Authors: Stovner, Bård Nagy, Johansen, Tor Arne
    Abstract:

    This paper considers the estimation of the steady wind component around small fixedwing unmanned aerial vehicles using measurements from a Pitot-Static Tube and velocity over ground information. A three-stage filter is proposed, which yields globally exponentially stable estimation of the wind velocity and a correction factor on the dynamic pressure measurements from the Pitot-Static Tube. The suggested filter is compared with an extended Kalman filter and shown to yield identical steady state performance in both simulations and experiments. Additionally, the improved stability with respect to the extended Kalman filter is demonstrated with a choice of suboptimal tuning, for which the extended Kalman filter failed to converge whereas the suggested filter did not

  • Real-Time Moving Horizon Estimation of Air Data Parameters and Wind Velocities for fixed-wing UAVs
    'Institute of Electrical and Electronics Engineers (IEEE)', 2020
    Co-Authors: Wenz, Andreas Wolfgang, Johansen, Tor Arne
    Abstract:

    We present a real-time implementation of an estimation algorithm for angle of attack, airspeed and wind velocities estimation on a single board computer. The estimator uses only sensor data from a standard fixed-wing UAV autopilot, which consists of a Global Navigation Satellite System receiver, an inertial measurement unit and a Pitot-Static Tube. This sensor data is fused with a combination of kinematic, aerodynamic and stochstic wind models in a nonlinear moving horizon estimator using numerical optimization. An algorithmic differentiation toolbox and automatic code generation is used to create a realtime capable estimator which is able to run within a UAV on an on-board computer. Hardware in the Loop simulation results show that the latency of the estimator is significantly below the expected wind gust period and gives low root-mean-square estimation errors for angle of attack (0.29◦ ) , airspeed (0.21m/s) and wind velocities (0.44m/s)

Wilujeng Cahyaningsih - One of the best experts on this subject based on the ideXlab platform.

  • STUDI EKSPERIMEN KARAKTERISTIK ALIRAN MELINTASI SILINDER SIRKULAR BERPENGGANGGU PRISMA SEGITGA SAMASISI, PRISMA SEGI EMPAT DAN SILINDER SIRKULAR Studi Kasus Variasi Jarak Longitudinal (S/D) = 1,75÷ 2,00
    2016
    Co-Authors: Wilujeng Cahyaningsih
    Abstract:

    Dalam kehidupan sehari-hari, aplikasi engineering sangat banyak digunakan dalam berbagai instalasi industri. Aplikasi engineering tersebut banyak yang berhubungan dengan aliran eksternal pada mekanika fluida. Salah satu peneletian aliran eksternal menarik adalah penelitian tentang aliran yang melintasi body berpengganggu. Pengaruh dari fenomena aliran melintasi body berpengganggu adalah terbentuknya wake seta drag force yang disebabkan oleh separasi aliran. Adanya gaya drag umumnya tidak diinginkan karena dapat mengurangi efisiensi energy. Salah satu pemanfaatan hasilnya adalah penggunaan konstruksi bangunan, fondasi bangunan off-shore dan jembatan agar didapat desain yang maksimum. Penelitian ini dilakukan secara eksperimen pada sebuah wind tunnel jenis subsonic dengan benda uji berupa seilinder utama dengan diameter 60 mm dan body pengganggu berbentuk prisma segitiga samasisi, prisma segiempat dan silinder dengan variasi jarak S/D = 1,75, 1,80, 1,85, 1,90, 1,95 dan 2,00.pengujian ini mengunakan bilangan Reynolds = 5,3 x 104 berdasarkan S/D dan kecepatan free stream. Karakteristik aliran berupa grafik Cp, u/Umaz , St dan CD diperoleh dengan mengukur distribusi tekanan pada kontur silinder utama, profil kecepatan dibelakang silinder frekuensi vortex shedding. Pengukuran distribusi tekanan menggunakan wall pressure tap yang dipasang di sekeliling silinder utama, pengukuran profil kecepatan menggunakan pitot static Tube pada jarak pengukuran x/D= 3. Untuk pengambilan data untuk perhitungan bilangan Strouhal dilakukan dengan menempatkan probe HWA padajarak x = 3D dan y = 1D. Metode Fast Fourier Transform (FFT) digunakan untuk mengubah domain waktu menjadi domain frekuensi sehingga diperoleh frekuensi vortex shedding. Hasil dari penelitian ini menunjukkan pengganggu yang paling efektif mengurangi gaya drag adalah pengganggu tipe B yang mampu mereduksi gaya drag sebesar 73,5% pada jarak S/D = 1.75. Hal ini disebabkan penambahan pengganggu mempercepat transisi lapis batas boundary layer silinder sirkular dari laminar menjadi turbulen. Turbulen boundary layer ini lebih efektif menahan adverse pressure serta gaya gesek yang terjadi kemudian mengakibatkan titik separasi mundur ke belakang dan daerah wake menyempit dan menurunkan drag force. The flow around circular cylinder has been subjected to intense research efforts in the past, mostly experiment but also by using numerical simulation. Different studies so that this flow configuration has many engineering application and still present one of the challenges in fluid mechanics, such as offshore risers, bridge piers, periscopes, chimney, towers, masts, stays, cables, antenne and wires. Therefore, it is still important to continue the study with circular cylinder as an object, especially on a group configuration. In order to reduce the drag coefficient of circular cylinder, same of methods were studied. This study is to present reducing of aerodynamics forces on a circular cylinder by upstream installation of some bluff bodies as passive control or disturbance, such as bodies Type A, Type B, Type C, Type D, and Type E. In order to reduce the drag force on a circular cylinder (D = 60 mm), five bluff bodies; Type A, B, C, D, and E having a diameter (d) or long side of 7,5 mm were used as a passive control. The passive control were located in various spacing positions of S/D = 1.75 ; 1.80 ; 1.85 ; 1.90 ; 1.95 and 2.00. The experiments were carried out in a subsonic open circuit windtunnel. This facility has a 1780 mm long, with test section 660mm x 660 mm. the frees stream velocity of wind tunnel could be adjusted constant to 13,6 m/s, corresponding to Reynolds number Re = 5,3x104 (base on diameter D and the free stream velocity). Seventy-two pressure taps with interval 50 were installed on the wall of the circular cylinder and connected to an inclined cerosine manometer, which it makes it possible to measure the pressure distribution around the circular cylinder. The velocity profile behind the circular cylinder was measured using a Pitot-Static Tube connected to the inclined manometer. The Pitot-Static Tube was placed at 18 cm at the rear of the axis of the cylinder or corresponding to x/d = 3, and finally frequency of vortex shadding behind the cylinder was measured at x/D = 3 and y/D = 1 by hot wire anemometer. The experimental result show that there is redaction of drag coefficient on main cylinder by upstream installation of the sum bluff body as passive control or cylinder disturbance. The passive control “Type B” at S/D = 1.75 gives has the higest drag reduction on the large circular cylinder situated downstream. It gives about 0.265 times the drag of a single cylinder

Tor Arne Johansen - One of the best experts on this subject based on the ideXlab platform.

  • moving horizon estimation of air data parameters for uavs
    IEEE Transactions on Aerospace and Electronic Systems, 2020
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    Local wind velocities, angle of attack, and lift coefficients of a fixed-wing unmanned aerial vehicle (UAV) are estimated by fusing kinematic, aerodynamic, and stochastic wind models with data from an inertial measurement unit, a global navigation satellite system receiver, and a Pitot-Static Tube in a moving horizon estimator. Experimental validation with two different UAVs and two sensor sets of different quality shows promising results for both wind velocity and angle of attack estimation.

  • Icing Detection for Small Fixed Wing UAVs using Inflight Aerodynamic Coefficient Estimation
    2019 IEEE Aerospace Conference, 2019
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    In cold and humid environments, airfoil icing is a major hindrance to UAV operations. Airfoil icing increases the aerodynamic drag coefficient, while reducing the maximum lift coefficient and the stall angle. This results in degraded endurance and safety of an UAV. Recently de-icing solutions for fixed-wing UAVs have been developed. These solutions use resistive heating in order to melt the ice on the wings. However, since this requires a high amount of energy it is desirable to only heat the wings if significant icing occurs. In this paper, a method for automatic icing detection is presented. A moving horizon estimator (MHE) is used, which combines aerodynamic, kinematic and stochastic wind models with data from a typical autopilot sensor suite to estimate angle of attack and lift coefficients. The sensor suite consists of an inertial measurement unit (IMU), a global navigation satellite system (GNSS) receiver, a heading reference and a Pitot-Static Tube. Within the MHE an Unscented Kalman Filter (UKF) is used for arrival cost approximation. FENSAP icing simulations show that in severe icing conditions, both the offset and the gradient of the lift coefficient change. Based on these icing simulations an UAV flight simulator that can simulate icing has been used. Simulation results show that the MHE is capable of monitoring changes in offset and gradient of the lift coefficient due to icing. A faster convergence to the estimated coefficient values could be achieved when using an external trigger signal, i.e. from a temperature and humidity sensor, to reset the covariance matrix of the arrival cost. We also investigate the effect on convergence speed resulting from an altitude change giving additional excitation. The estimation results show angle of attack estimation errors below 1 degree. These estimates can be used to limit the angle of attack and adjust the commanded airspeed in the autopilot in order to avoid stall.

Yhasmin Salma - One of the best experts on this subject based on the ideXlab platform.

  • Studi Eksperimen Tentang Karakteristik Aliran Pada Silinder Sirkular Yang Diganggu Oleh Prisma Segitiga Samasisi, Prisma Segiempat Samasisi, Dan Silinder Sirkular (Studi Kasus Untuk Variasi Jarak [S/D] = 0,9-1,15)
    2015
    Co-Authors: Yhasmin Salma
    Abstract:

    Masalah dibidang aerodinamika dari beberapa struktur medan aliran telah sering mendapat perhatian dari para engineer dan investigatior lainnya selama beberapa dekade . Berbagai penelitian yang berbeda menunjukkan bahwa konfigurasi aliran ini memiliki banyak aplikasi dibidang teknik dan masih ada contoh permasalahan salah satunya adalah tantangan dalam mekanika fluida, seperti riser lepas pantai, dermaga jembatan, menara, tiang, dll. Oleh karena itu, pentingnya untuk melanjutkan penelitian pada silinder sirkular sebagai obyek, terutama pada konfigurasi kelompok. Penelitian ini adalah untuk memberikan informasi bagaimana suatu aliran mengurangi gaya aerodinamis pada silinder sirkular dengan melakukan pengontrolan secara pasif , seperti prisma segi empat diputar 0º ( Tipe A ) , prisma empat persegi panjang diputar 45º (Tipe B ) , segitiga prisma diputar 30º (Tipe C ) , prisma segitiga diputar 210º (Tipe D ) , dan silinder sirkuler (Tipe E ) . Penelitian ini dilakukan secara eksperimen pada sebuah wind tunnel jenis subsonic open circuit dengan benda uji berupa seilinder utama dengan diameter 60 mm dan 7,5 mm pada body pengganggu tipe A, tipe B, tipe C, tipe D, dan tipe E dengan variasi jarak S/D = 0,90, 0,95, 1,00, 1,05, 1,10 dan 1,15. Pengujian ini dilakukan pada wind tunnel berjenis subsonic open circuit wind tunnel dengan panjang 1780 mm dan ukuran pada ii ii test section wind tunnel 660 mm x 660 mm. Kecepatan freestream pada wind tunnel diambil konstan pada 13,88 m/s pada saat dilakukan pengambilan data dengan Reynolds Number 5,3 x 104. Pengukuran distribusi tekanan menggunakan 72 buah titik pada wall pressure tap dengan jarak 5º tiap sudut yang dipasang disekeliling silinder utama, pengukuran profil kecepatan menggunakan pitot static Tube pada jarak pengukuran x/D= 3 kemudian pengambilan data untuk perhitungan bilangan Strouhal dilakukan dengan menempatkan probe HWA pada jarak x = 3D dan y = 1D . Pada penelitian ini, dapat mengetahui gaya drag yang dihasilkan pada silinder utama dengan diberi pengganggu sebagai pengontrol pasif. Hal ini mengindikasikan bahwa silinder Tipe B pada jarak S/D 1,15 paling efektif dalam menurunkan gaya drag dibelakang silinder utama, penurunan sebesar 0,27 kali pada silinder tanpa pengganggu. ============= The aerodynamic problem of multiple structures in a flow field have frequently received the attention of engineer and other investigatiors for saveral decades. Different studies show that this flow configuration has many engineering application and still present one of the challenges in fluid mechanics, such as offshore riser, bridge piers, towers, mast and stays, etc. Therefore, it is still important to continue the study with circular cylinder as an object, especially on a group configuration. This study is to present the reducing of aerodynamics forces on a circular cylinder by upstream installation of some bluff bodies as passive control or disturbance, such as rectangular prism is rotated 0º (Type A), rectangular prism is rotated 45º (Type B), triangular prism is rotated 30º (Type C), triangular prism is rotated 210º (Type D), and circular cylinder (Type E). In order to reduce the drag force on a circular cylinder (D= 60 mm), five bluff body; type A, B, C, D, and E having a diameter (d) or long side of 7.5 mm were used as a passive control. The passive control were located in various spacing position of S/D = 0.9, 0.95, 1.0, 1.05, 1.1, and 1.15. The experiment were carried out in a subsonic open circuit wind tunnel. This facility has a 1780 mm long, with test section 660 mm x 660 mm. The free same velocity of wind tunnel could be iv adjusted constant to 13.88 m/s, corresponding to Reynolds number Re = 5.3 x 104 (based on diameter D and the free stream velocity). Seventy-two pressure taps with interval 5º were installed on the wall of the circular cylinder and connected to an inclined kerosene manometer, which it makes it possible to measure the pressure distribution around the circular cylinder. The velocity profile behind the circular cylinder was measured using a Pitot-Static Tube connected to inclined manometer. The Pitot-Static Tube was placed at 18 cm at the rear of the axis of the cylinder or correspondin to x/d = 3, and finally frequencyof vortex shedding behind the cylinder was measured at x/D = 3 and y/D = 1 by hot wire anemometer. The experiment result show that there is reduction of drag coefficient on main cylinder by upstream installation of the some bluff body as passive control or cylinder disturbance. The passive control “type B” at S/D 1.15 gives the highest darg reduction on the larger circular cylinder situated downstream. It gives about 0.27 times the drag of a single cylinder