scholarly journals Turbulent Length Scales in a Fast-flowing, Weakly Stratified, Strait: Cook Strait, New Zealand

2017 ◽  
Author(s):  
Craig L. Stevens
Keyword(s):  
New Zealand ◽  
Full Range ◽  
Turbulent Energy ◽  
Flow Speed ◽  
Turbulent Dissipation ◽  
Dissipation Rates ◽  
Cook Strait ◽  
Flow Speeds ◽  
Ozmidov Scale ◽  
Thorpe Scale

Abstract. There remains much to be learned about the full range of turbulent motions in the ocean. Here we consider turbulence and overturn scales in the relatively shallow, weakly stratified, fast-flowing tidal flows of Cook Strait, New Zealand. With flow speeds reaching 3 m s−1 in a water column of ~ 300 m depth the location is heuristically known to be highly turbulent. Dissipation rates of turbulent kinetic energy ε along with the Thorpe scale, LT, are described. Thorpe scales, often as much as one quarter of the water depth, are compared with dissipation rates and background flow speed. Turbulent energy dissipation rates ε are modest but high for oceans, around 5 × 10–5 W kg−1. Comparison of the buoyancy-limit Ozmidov scale LOz suggest the Cook Strait data lie for the majority of the time in the LOz > LT regime, but not universally. Also, comparison of direct and LT -based estimates of ε exhibit reasonable similarity.

scholarly journals Turbulent length scales in a fast-flowing, weakly stratified, strait: Cook Strait, New Zealand

Ocean Science ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 801-812 ◽  
Author(s):  
Craig L. Stevens
Keyword(s):  
New Zealand ◽  
Full Range ◽  
Turbulent Energy ◽  
Flow Speed ◽  
Turbulent Dissipation ◽  
Dissipation Rates ◽  
Cook Strait ◽  
Flow Speeds ◽  
Ozmidov Scale ◽  
Thorpe Scale

Abstract. There remains much to be learned about the full range of turbulent motions in the ocean. Here we consider turbulence and overturn scales in the relatively shallow, weakly stratified, fast-flowing tidal flows of Cook Strait, New Zealand. With flow speeds reaching 3 m s−1 in a water column of ∼300 m depth the location is heuristically known to be highly turbulent. Dissipation rates of turbulent kinetic energy ε, along with the Thorpe scale, LT, are described. Thorpe scales, often as much as one-quarter of the water depth, are compared with dissipation rates and background flow speed. Turbulent energy dissipation rates ε are modest but high for oceans, around 5×10-5 W kg−1. Comparison of the buoyancy-limit Ozmidov scale LOz suggest the Cook Strait data lie for the majority of the time in the LOz > LT regime, but not universally. Also, comparison of direct and LT-based estimates of ε exhibit reasonable similarity.

scholarly journals Discontinuities and Alfvénic fluctuations in the solar wind

2013 ◽  
Vol 31 (5) ◽  
pp. 871-887 ◽  
Author(s):  
G. Paschmann ◽  
S. Haaland ◽  
B. Sonnerup ◽  
T. Knetter
Keyword(s):  
Solar Wind ◽  
Full Range ◽  
Flow Speed ◽  
Reduced Form ◽  
Angular Deviation ◽  
Cluster Data ◽  
Flow Speeds ◽  
Wind Velocities ◽  
Two Sides ◽  
Average Angle

Abstract. We examine the Alfvénicity of a set of 188 solar wind directional discontinuities (DDs) identified in the Cluster data from 2003 by Knetter (2005), with the objective of separating rotational discontinuities (RDs) from tangential ones (TDs). The DDs occurred over the full range of solar wind velocities and magnetic shear angles. By performing the Walén test in the de Hoffmann–Teller (HT) frame, we show that 77 of the 127 crossings for which a good HT frame was found had plasma flow speeds exceeding 80% of the Alfvén speed at an average angular deviation of 7.7°; 33 cases had speeds exceeding 90% of the Alfvén speed at an average angle of 6.4°. We show that the angular deviation between flow velocity (in the HT frame) and the Alfvén velocity can be obtained from a reduced form of the Walén correlation coefficient. The corresponding results from the Walén test expressed in terms of jumps in flow speed and corresponding jumps in Alfvén speed are similar: 66 of the same 127 cases had velocity jumps exceeding 80% with average angular deviation of 5.8°, and 22 exceeding 90% of the jump in Alfvén speed, with average angular deviation 6.2°. We conclude that a substantial fraction of the 127 events can be identified as RDs. We present further evidence for coupling across the DDs by showing that, for most of the 127 crossings, the HT frame velocities, evaluated separately on the two sides of the DD, are nearly the same – a result required for RDs but not for TDs. We also show that the degree of Alfvénicity is nearly the same for the DDs and fluctuations in which the DDs are embedded. Whatever process causes deviations from ideal Alfvénicity appears to operate equally for the DDs as for the surrounding fluctuations. Finally, our study has established a unique relation between the strahl electron pitch angle and the sign of the Walén slope, implying antisunward propagation in the plasma frame for all 127 cases.

scholarly journals TURBULENT MIXING PROCESSES IN LABANI CHANNEL, THE MAKASSAR STRAIT

2016 ◽  
Vol 8 (1) ◽  
Author(s):  
Yuli Naulita
Keyword(s):  
Turbulent Mixing ◽  
Eddy Diffusivity ◽  
Turbulent Energy ◽  
Wavelet Denoising ◽  
Mixing Processes ◽  
Ozmidov Scale ◽  
Thorpe Scale ◽  
Order Of Magnitude ◽  
O 10 ◽  
Temperature Depth

<p><em>Study on turbulent mixing processes in Labani Channel, the Makassar Strait, was conducted by using the INSTANT (International Nusantara Stratification And Transport) program dataset, in Juli 2005. The turbulent mixing process was evaluated using Thorpe method, where the overturning eddies were revealed by density inversions in CTD (Conductivity Temperature Depth) profiles. All individual identified-overturn regions was validated by the GK’s test (Galbraith and Kelly test) where at first noise on CTD signals had been removed  by applying wavelet denoising.   A large number of overturn regions with Thorpe scale (L<sub>T</sub>) less than 0.5 m were detected in the thermocline layer of Makassar Strait. Based on linear relationship between Thorpe and Ozmidov scale, order of magnitude of the turbulent energy kinetic dissipation rate in Labani Channel was estimated about </em><em>10<sup>-11</sup>- 10<sup>-5</sup>Wkg<sup>-1</sup> and </em><em>density eddy diffusivity K<sub>ρ</sub></em><em>(10<sup>-6  </sup>– 10<sup>-2</sup>) m<sup>2</sup>/s . The strong of turbulen mixing was found at the layer of  NPSW at 150 m depth and NPIW at 300 m depth, indicated by high values of K<sub>ρ </sub> (O = 10<sup>-3</sup> – 10<sup>-2</sup> m<sup>2</sup>s<sup>-1</sup>).  It reveals that turbulent mixing has an important role on determining ITF water mass character.  </em></p><p><strong><em>Keywoods</em></strong><em>: turbulent mixing, wavelet denoising, overturn region, Thorpe method, Labani Channel, Makassar Srait.</em></p>

scholarly journals TURBULENT MIXING PROCESSES IN LABANI CHANNEL, THE MAKASSAR STRAIT

2016 ◽  
Vol 8 (1) ◽  
pp. 345-355 ◽  
Author(s):  
Yuli Naulita
Keyword(s):  
Turbulent Mixing ◽  
Eddy Diffusivity ◽  
Turbulent Energy ◽  
Wavelet Denoising ◽  
Mixing Processes ◽  
Ozmidov Scale ◽  
Thorpe Scale ◽  
Order Of Magnitude ◽  
O 10 ◽  
Temperature Depth

Study on turbulent mixing processes in Labani Channel, the Makassar Strait, was conducted by using the INSTANT (International Nusantara Stratification And Transport) program dataset, in Juli 2005. The turbulent mixing process was evaluated using Thorpe method, where the overturning eddies were revealed by density inversions in CTD (Conductivity Temperature Depth) profiles. All individual identified-overturn regions was validated by the GK’s test (Galbraith and Kelly test) where at first noise on CTD signals had been removed  by applying wavelet denoising.   A large number of overturn regions with Thorpe scale (LT) less than 0.5 m were detected in the thermocline layer of Makassar Strait. Based on linear relationship between Thorpe and Ozmidov scale, order of magnitude of the turbulent energy kinetic dissipation rate in Labani Channel was estimated about 10-11- 10-5Wkg-1 and density eddy diffusivity Kρ(10-6  – 10-2) m2/s . The strong of turbulen mixing was found at the layer of  NPSW at 150 m depth and NPIW at 300 m depth, indicated by high values of Kρ  (O = 10-3 – 10-2 m2s-1).  It reveals that turbulent mixing has an important role on determining ITF water mass character.  Keywoods: turbulent mixing, wavelet denoising, overturn region, Thorpe method, Labani Channel, Makassar Srait.

A Red Water Bloom of Rotifers in Cook Strait, New Zealand

Nature ◽  
1960 ◽  
Vol 186 (4721) ◽  
pp. 328-329 ◽  
Author(s):  
VIVIENNE CASSIE
Keyword(s):  
New Zealand ◽  
Water Bloom ◽  
Cook Strait

scholarly journals Observations of Turbulence in Free Atmosphere by Balloon-Borne Sensors

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3273
Author(s):  
Lesong Zhou ◽  
Zheng Sheng ◽  
Qixiang Liao
Keyword(s):  
Large Scale ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Sensor Data ◽  
Free Atmosphere ◽  
Height Range ◽  
High Latitude Region ◽  
Thorpe Scale ◽  
Scale Turbulence ◽  
Turbulence Parameters

In recent years, Thorpe analysis has been used to retrieve the characteristics of turbulence in free atmosphere from balloon-borne sensor data. However, previous studies have mainly focused on the mid-high latitude region, and this method is still rarely applied at heights above 30 km, especially above 35 km. Therefore, seven sets of upper air (>35 km) sounding data from the Changsha Sounding Station (28°12′ N, 113°05′ E), China are analyzed with Thorpe analysis in this article. It is noted that, in the troposphere, Thorpe analysis can better retrieve the turbulence distribution and the corresponding turbulence parameters. Also, because of the thicker troposphere at low latitudes, the values of the Thorpe scale L T and turbulent energy dissipation rate ε remain greater in a larger height range. In the stratosphere below the height of 35 km, the obtained ε is higher, and Thorpe analysis can only be used to analyze the characteristics of large-scale turbulence. In the stratosphere at a height of 35–40 km, because of the interference of sensor noise, Thorpe analysis can only help to retrieve the rough distribution position of large-scale turbulence, while it can hardly help with the calculation of the turbulence parameters.

scholarly journals Large amplitude, short wave peristalsis and its implications for transport

2015 ◽  
Author(s):  
Lindsay D Waldrop ◽  
Laura A. Miller
Keyword(s):  
Fluid Flow ◽  
Large Amplitude ◽  
Compression Wave ◽  
Wave Speed ◽  
Flow Direction ◽  
Short Wave ◽  
Flow Speed ◽  
Biological Pumps ◽  
Flow Speeds ◽  
Flow Compression

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow are often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a non-linear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate uni-directionally along a tube without the need for a structurally fixed flow direction.

scholarly journals "So We Thought not to Lose Our Background Completely": Agency and Belonging among South Sudanese Acholi in New Zealand

2021 ◽  
Author(s):  
◽  
Ryan O'Byrne
Keyword(s):  
New Zealand ◽  
Cultural Practices ◽  
Participant Observation ◽  
Full Range ◽  
Fundamental Aspect ◽  
Cultural Performance ◽  
The South ◽  
Community Members ◽  
South Sudanese ◽  
Background Population

<p>The members of the South Sudanese Acholi population in New Zealand are part of the burgeoning number of refugees worldwide. As such, they are at risk of having their personal experiences submerged in the stereotypical view of ‘the refugee experience’. The South Sudanese Acholi community are a small but distinct ethnic sub-community within the wider South Sudanese refugee-background population in New Zealand. One of my primary aims in this thesis is to represent the specifically-situated experiences of individuals from this group within the broader contexts of refugee resettlement. A fundamental aspect of these experiences is the ambiguous and often contradictory senses of belonging which community members describe. Using analysis of the narratives through which these individuals make sense of their resettlement experiences, I determine agency to be an important consideration in experiences of belonging and, therefore, I argue that the role of agency to belonging should be more widely recognised. In this thesis I demonstrate how various attempts by South Sudanese Acholi at cultural (re)production in New Zealand are intimately linked to the many difficulties these individuals experience in resettlement, and particularly to how these difficulties impact the development and maintenance of a sense of belonging. Analyses of individual and common factors demonstrate the importance of belonging to experiences of resettlement. This is apparent throughout all aspects of South Sudanese Acholi’s everyday lives. This thesis is organised around the interlinking nature of three aspects of everyday life: marriage, cultural performance, and discursive practices. A central unifying factor is that each of these aspects of every day experience can be understood as attempts in developing more stable senses of belonging. Data was collected through a combination of participant observation and unstructured interviews. Participant observation was primarily undertaken among the Sudanese Acholi Cultural Association (SACA), a community-organised Acholi cultural performance group. Although not exclusively the focus of this research, the members of this group comprise the basis of my research participants and their resettlement experiences form the basis for my results. A focus on participants’ stories about their lives in resettlement allows analysis of the importance of their everyday practices and perceptions to the ways in which they experience and understand their lives in New Zealand and demonstrates that the on-going interaction between their experiences as refugees and their resettlement experiences are mutually reinforcing. I suggest that if refugees’ own voices and opinions are to be accurately represented, a holistic perspective of the full range of their experiences is required. The ambivalent, multiple, and multifaceted nature of belonging described by South Sudanese Acholi individuals’ is a defining feature of their resettlement experiences. I suggest that South Sudanese Acholi attempts at performing and reproducing their customary cultural practices in New Zealand serve primarily as creative means of adapting to the conditions of resettlement in ways which allow the construction, development, and maintenance of feelings of belonging among community members. However, I also determine that lack of agency is especially important for understanding the ambivalence about belonging South Sudanese Acholi demonstrate when speaking of these resettlement experiences. I argue that behind many of the everyday actions taken by refugees are simultaneous attempts to rediscover a sense of agency and to recreate a foundation for belonging.</p>

scholarly journals What Should Constitute Infringement of a Non-Traditional Mark?

2018 ◽  
pp. 165-184
Author(s):  
Michael Handler
Keyword(s):  
New Zealand ◽  
Full Range ◽  
Third Parties ◽  
Third Party ◽  
Registration System ◽  
Product Features ◽  
Breathing Room ◽  
Trademark Use

Various “defensive doctrines” might be employed to create space for third parties wishing to make legitimate use of features of registered non-traditional marks. This chapter explores one such doctrine: a requirement that infringing use be “use as a trademark.” This doctrine, as it has been developed in countries such as Australia and New Zealand in cases involving non-traditional marks, is more complex than is often appreciated. At times it has been stretched to accommodate worthy policy considerations, which has caused tensions with other aspects of the registration system. At other times it has been applied too restrictively, unduly limiting the scope of permissible third party use of product features. The chapter offers suggestions as to how “trademark use” might be recalibrated to manage the full range of concerns raised by non-traditional marks, in a manner that affords owners adequate protection while leaving sufficient breathing room for third party users.

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