Power Number and Mixing Drag Coefficient of Koch Fractal Impellers used by Koch Curve

2021 ◽  
Vol 47 (3) ◽  
pp. 57-63
Author(s):  
Kazumi Suzukawa ◽  
Kazuki Tomoda ◽  
Tatsufumi Miyazaki ◽  
Yusuke Kawamura ◽  
Yugo Kanai
Keyword(s):  
Drag Coefficient ◽  
Koch Curve ◽  
Power Number ◽  
Koch Fractal

scholarly journals Modified Koch Fractal Antenna for Multi and Wideband Wireless Applications

2021 ◽  
Vol 19 (2) ◽  
pp. 182-189
Author(s):  
Shweta Rani ◽  
Sushil Kakkar
Keyword(s):  
Numerical Simulations ◽  
Impedance Matching ◽  
Optimization Procedure ◽  
Design Parameters ◽  
Impedance Bandwidth ◽  
Fractal Antenna ◽  
Bacterial Foraging Optimization ◽  
Koch Curve ◽  
Wireless Applications ◽  
Koch Fractal

This paper focuses on the design and development of modified Koch fractal antenna. Compared to traditional Koch curve antenna, the presented antenna possesses a greater number of frequency bands and better impedance matching. Furthermore, the bacterial foraging optimization (BFO) approach is implemented to enhance the impedance bandwidth. The developed technique has been verified by employing various numerical simulations. The design parameters generated from the optimization procedure have been utilized to manufacture the antenna and the respective experimental and simulated results compared. The measured results show that the designed antenna exhibits multi and wideband behavior, covering WLAN, WIMAX, and various other wireless applications.

Compact Circular CSRR Loaded Koch Fractal Inspired Frequency Band Reconfigurable Antenna

2020 ◽  
pp. 2150075
Author(s):  
Puspendu Bikash Saha ◽  
Dibyendu Ghoshal ◽  
Rajib Kumar Dash
Keyword(s):  
Frequency Band ◽  
Ground Plane ◽  
Resonance Mode ◽  
Ring Resonators ◽  
Koch Curve ◽  
Fractal Curve ◽  
Operating Modes ◽  
Resonance Modes ◽  
Rectangular Patch ◽  
Koch Fractal

A compact frequency band reconfigurable dual-mode antenna utilizing both Koch fractal geometry and circular complementary split ring resonators (CSRRs) is presented in this paper. The proposed antenna can be electrically switched into both dual- and single-band resonance modes. A Koch curve derivative novel fractal curve is used to design the patch boundary of the antenna. Two optimized circular CSRRs are loaded inside the antenna geometry to achieve double-band resonance. The antenna operates at both 5.1[Formula: see text]GHz (upper WLAN band) and 9.6[Formula: see text]GHz ([Formula: see text]-band) in dual resonance mode and resonates only at 8[Formula: see text]GHz ([Formula: see text]-band) in single resonance mode. A properly biased RF-range PIN diode placed at the slotted ground plane reconfigures the antenna in two operating modes by switching into its ON–OFF states. The antenna is fabricated on cost-efficient epoxy (FR-4) substrate consuming the maximum dimension of [Formula: see text] which is much more compact than the conventional rectangular patch antennas designed for similar bands. Stable radiation characteristics with reduced cross-polarization are achieved at all the resonant bands of the antenna. A prototype of the proposed antenna is fabricated and measured. The simulated results are in good agreement with the measured ones.

A Symbolic Dynamics Approach to Random Walk on Koch Fractal

2014 ◽  
Vol 610 ◽  
pp. 17-22
Author(s):  
Hong Luo ◽  
Ying Tan ◽  
Shou Li Peng
Keyword(s):  
Random Walk ◽  
Hausdorff Measure ◽  
Symbolic Sequence ◽  
Koch Curve ◽  
One Dimensional ◽  
Underlying Space ◽  
Chemical Distance ◽  
Koch Fractal ◽  
The One ◽  
Partition Of Integer

The paper presents a new symbolic dynamic approach to the research of the random walk andBrownianmotion(BM)on Koch fractal. From the symbolic sequence of Koch automaton, on the one hand, we obtained the geometric description of the Koch curve completely, and constructed the state space of the random walk with the symbolic sequence. And the precise arithmetic representation of Koch curve is provided by the deterministicRademachersequence. On the other hand, the arithmetic feature of the Koch automaton, the position numbers, forms a partition of integer , which is naturally a one-dimensional lattice, it will be underlying space of theBMdirectly. When the chemical distance is introduced to measure the distance between two states, analytic results of the model for random walk on Koch fractal are obtained, particularly the relation between the chemical distance and the Hausdorff measure is discussed, and the Wiener Process in terms of Hausdorff measure is constructed parallel.

Bulk drag coefficient of a subaquatic vegetation subjected to irregular waves: Influence of Reynolds and Keulegan-Carpenter numbers

2020 ◽  
pp. 34-42
Author(s):  
Thibault Chastel ◽  
Kevin Botten ◽  
Nathalie Durand ◽  
Nicole Goutal
Keyword(s):  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Empirical Relationship ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Geometrical Parameters ◽  
Flume Experiments ◽  
Seagrass Meadows ◽  
Artificial Vegetation

Seagrass meadows are essential for protection of coastal erosion by damping wave and stabilizing the seabed. Seagrass are considered as a source of water resistance which modifies strongly the wave dynamics. As a part of EDF R & D seagrass restoration project in the Berre lagoon, we quantify the wave attenuation due to artificial vegetation distributed in a flume. Experiments have been conducted at Saint-Venant Hydraulics Laboratory wave flume (Chatou, France). We measure the wave damping with 13 resistive waves gauges along a distance L = 22.5 m for the “low” density and L = 12.15 m for the “high” density of vegetation mimics. A JONSWAP spectrum is used for the generation of irregular waves with significant wave height Hs ranging from 0.10 to 0.23 m and peak period Tp ranging from 1 to 3 s. Artificial vegetation is a model of Posidonia oceanica seagrass species represented by slightly flexible polypropylene shoots with 8 artificial leaves of 0.28 and 0.16 m height. Different hydrodynamics conditions (Hs, Tp, water depth hw) and geometrical parameters (submergence ratio α, shoot density N) have been tested to see their influence on wave attenuation. For a high submergence ratio (typically 0.7), the wave attenuation can reach 67% of the incident wave height whereas for a low submergence ratio (< 0.2) the wave attenuation is negligible. From each experiment, a bulk drag coefficient has been extracted following the energy dissipation model for irregular non-breaking waves developed by Mendez and Losada (2004). This model, based on the assumption that the energy loss over the species meadow is essentially due to the drag force, takes into account both wave and vegetation parameter. Finally, we found an empirical relationship for Cd depending on 2 dimensionless parameters: the Reynolds and Keulegan-Carpenter numbers. These relationships are compared with other similar studies.

Numerical Comparison of Drag Coefficient between Nacelle Lip-Skin with and without Bias Acoustic Liner

2016 ◽  
Vol 10 (6) ◽  
pp. 390 ◽  
Author(s):  
Qummare Azam ◽  
Mohd Azmi Ismail ◽  
Nurul Musfirah Mazlan ◽  
Musavir Bashir
Keyword(s):  
Drag Coefficient ◽  
Numerical Comparison ◽  
Acoustic Liner

EFFECT OF THE MACRO-SCALE TOPOLOGY OVER THE EFFECTIVE DRAG COEFFICIENT IN DENSE GAS-SOLID FLUIDIZED FLOWS

2018 ◽  
Author(s):  
Seyed Reza Amini Niaki ◽  
Joseph Mouallem ◽  
Christian Milioli ◽  
Fernando Milioli
Keyword(s):  
Drag Coefficient ◽  
Dense Gas ◽  
Macro Scale

Surface Aeration Threshold in Agitated Vessels

1996 ◽  
Vol 61 (5) ◽  
pp. 681-690
Author(s):  
Kamil Wichterle ◽  
Tomáš Svěrák
Keyword(s):  
Simple Model ◽  
Liquid Surface ◽  
Power Input ◽  
Power Number ◽  
Region Analysis ◽  
Surface Aeration ◽  
Liquid Dispersion ◽  
Mixing Vessels ◽  
Number Curve

Violent agitation of liquids in mixing vessels may result in the regime of surface aeration being attained when the bubbles formed at the liquid surface enter the impeller region. Analysis of data on surface aeration for different liquids in a set of geometrically similar agitated vessels is presented. Data on the just aerated state as observed visually in transparent liquids, and data for the efficient aeration as determined from the break on the power number curve are considered. A simple model is developed for correlation of the data which enables the threshold of aeration to be predicted from the value of the recirculation number Nc = Nd (ρ/σg)1/4. The possibility of interpreting various literature data for the aeration threshold and for the power input with use of Nc is demonstrated. Similar modelling rules hold also for the correlation of beginning of the efficient liquid-liquid dispersion.

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