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62-513: The Elcho Shield is an annual long range shooting competition between national teams of eight from England , Scotland , Ireland and Wales . The trophy holder was originally able to choose the venue of the competition, however, since the NRA 's move to Surrey from Wimbledon in 1890, the competition has been held at National Shooting Centre , Bisley in Surrey , England. It is usually contested during

124-399: A supersonic bullet known as a bullet trace , due to turbulences creating visible refractive disturbances in the air. A bullet trace should not be confused with a vapor trail , which is sometimes observed when firing under rare conditions due to changes in air pressure around the bullet. While the bullet trace is usually only observable directly from behind the shooter, a vapor trail from

186-416: A balance between speed and precision , often involving movement and shooting from unusual positions with a time limit, at both known and unknown distances. Shooting distances can vary from between 10 and 1,000 meters / yards , and therefore the competitor must know the ballistics of his firearm very well. A competition usually consists of several courses of fire, and requires some physical activity since

248-411: A bullet is observable from any direction. Some believe you really get "the feel" of long range shooting when you have time to see the bullet fly towards the target, and then dive below or swing past, just when you were sure you would hit it. Weather conditions may also affect what is considered long range for a given firearm configuration. For instance a professional shooter may be able to repeatably hit

310-525: A constitutive relation between a turbulent flux and the gradient of a mean variable similar to the relation between flux and gradient that exists for molecular transport. In the best case, this assumption is only an approximation. Nevertheless, the turbulent diffusivity is the simplest approach for quantitative analysis of turbulent flows, and many models have been postulated to calculate it. For instance, in large bodies of water like oceans this coefficient can be found using Richardson 's four-third power law and

372-506: A given size target, i.e. a 100 mm ring, at 1000 meters (0.1 mil target difficulty) in low and predictable wind, while the same 100 mm target may be near impossible to hit in heavy and varying wind at 200 meters (0.5 mil target difficulty). A spotting scope is often used to observe hits and provide ballistic corrections, and can aid in seeing bullet trace. Bullet trace can often easily be seen in humid weather, but also on cool and sunny days. There are several possible explanations of

434-416: A mean value: and similarly for temperature ( T = T + T′ ) and pressure ( P = P + P′ ), where the primed quantities denote fluctuations superposed to the mean. This decomposition of a flow variable into a mean value and a turbulent fluctuation was originally proposed by Osborne Reynolds in 1895, and is considered to be the beginning of the systematic mathematical analysis of turbulent flow, as

496-457: A statistical description is needed. The Russian mathematician Andrey Kolmogorov proposed the first statistical theory of turbulence, based on the aforementioned notion of the energy cascade (an idea originally introduced by Richardson ) and the concept of self-similarity . As a result, the Kolmogorov microscales were named after him. It is now known that the self-similarity is broken so

558-400: A sub-field of fluid dynamics. While the mean values are taken as predictable variables determined by dynamics laws, the turbulent fluctuations are regarded as stochastic variables. The heat flux and momentum transfer (represented by the shear stress τ ) in the direction normal to the flow for a given time are where c P is the heat capacity at constant pressure, ρ is the density of

620-443: A third hypothesis of Kolmogorov was that at very high Reynolds number the statistics of scales in the range η ≪ r ≪ L are universally and uniquely determined by the scale r and the rate of energy dissipation ε . The way in which the kinetic energy is distributed over the multiplicity of scales is a fundamental characterization of a turbulent flow. For homogeneous turbulence (i.e., statistically invariant under translations of

682-434: A universal constant. This is one of the most famous results of Kolmogorov 1941 theory, describing transport of energy through scale space without any loss or gain. The Kolmogorov five-thirds law was first observed in a tidal channel, and considerable experimental evidence has since accumulated that supports it. Outside of the inertial area, one can find the formula below : In spite of this success, Kolmogorov theory

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744-445: A vector r (since the turbulence is assumed isotropic, the flow velocity increment depends only on the modulus of r ). Flow velocity increments are useful because they emphasize the effects of scales of the order of the separation r when statistics are computed. The statistical scale-invariance without intermittency implies that the scaling of flow velocity increments should occur with a unique scaling exponent β , so that when r

806-448: A wide range of length scales and the hierarchy can be described by the energy spectrum that measures the energy in flow velocity fluctuations for each length scale ( wavenumber ). The scales in the energy cascade are generally uncontrollable and highly non-symmetric. Nevertheless, based on these length scales these eddies can be divided into three categories. The integral time scale for a Lagrangian flow can be defined as: where u ′

868-430: Is a factor in developing turbulent flow. Counteracting this effect is the viscosity of the fluid, which as it increases, progressively inhibits turbulence, as more kinetic energy is absorbed by a more viscous fluid. The Reynolds number quantifies the relative importance of these two types of forces for given flow conditions, and is a guide to when turbulent flow will occur in a particular situation. This ability to predict

930-466: Is a range of scales (each one with its own characteristic length r ) that has formed at the expense of the energy of the large ones. These scales are very large compared with the Kolmogorov length, but still very small compared with the large scale of the flow (i.e. η ≪ r ≪ L ). Since eddies in this range are much larger than the dissipative eddies that exist at Kolmogorov scales, kinetic energy

992-723: Is a rapidly growing long range shooting discipline internationally governed by the International Confederation of Fullbore Rifle Associations . F-Class carry many similarities to traditional high power rifle , except that it is only fired at distances between 300 and 1200 yards (or meters), and the targets are half the size of regular targets. They compete in two categories: The ideal scope sight magnification for different types of long range shooting depends on application, scope quality and user preference. Different applications may have different shooting distances, light conditions, target sizes and target contrast against

1054-405: Is at present under revision. This theory implicitly assumes that the turbulence is statistically self-similar at different scales. This essentially means that the statistics are scale-invariant and non-intermittent in the inertial range. A usual way of studying turbulent flow velocity fields is by means of flow velocity increments: that is, the difference in flow velocity between points separated by

1116-409: Is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason, turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. The onset of turbulence can be predicted by

1178-410: Is characterized by a hierarchy of scales through which the energy cascade takes place. Dissipation of kinetic energy takes place at scales of the order of Kolmogorov length η , while the input of energy into the cascade comes from the decay of the large scales, of order L . These two scales at the extremes of the cascade can differ by several orders of magnitude at high Reynolds numbers. In between there

1240-431: Is characterized by the following features: Turbulent diffusion is usually described by a turbulent diffusion coefficient . This turbulent diffusion coefficient is defined in a phenomenological sense, by analogy with the molecular diffusivities, but it does not have a true physical meaning, being dependent on the flow conditions, and not a property of the fluid itself. In addition, the turbulent diffusivity concept assumes

1302-400: Is considerable evidence that turbulent flows deviate from this behavior. The scaling exponents deviate from the ⁠ n / 3 ⁠ value predicted by the theory, becoming a non-linear function of the order n of the structure function. The universality of the constants have also been questioned. For low orders the discrepancy with the Kolmogorov ⁠ n / 3 ⁠ value

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1364-416: Is considered long range. For centerfire intermediate rifle calibers, some might say that everything over 300 to 400 metres (330 to 440 yd) is considered long range, while some may claim that long range "starts" at 500 metres (550 yd). At the longer ranges the bullets will have a longer flight time, and on days with good lighting and weather conditions one can even see a brief trail of wake behind

1426-419: Is essentially not dissipated in this range, and it is merely transferred to smaller scales until viscous effects become important as the order of the Kolmogorov scale is approached. Within this range inertial effects are still much larger than viscous effects, and it is possible to assume that viscosity does not play a role in their internal dynamics (for this reason this range is called "inertial range"). Hence,

1488-467: Is fluid motion characterized by chaotic changes in pressure and flow velocity . It is in contrast to laminar flow , which occurs when a fluid flows in parallel layers with no disruption between those layers. Turbulence is commonly observed in everyday phenomena such as surf , fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence

1550-473: Is governed by the random walk principle. In rivers and large ocean currents, the diffusion coefficient is given by variations of Elder's formula. Via this energy cascade , turbulent flow can be realized as a superposition of a spectrum of flow velocity fluctuations and eddies upon a mean flow . The eddies are loosely defined as coherent patterns of flow velocity, vorticity and pressure. Turbulent flows may be viewed as made of an entire hierarchy of eddies over

1612-691: Is large and distinctive, made from a sheet of iron decorated with repousse scenes to a design by the artist G. F. Watts . It was presented to the National Rifle Association by its founder and president, Lord Elcho . This article related to sport in England is a stub . You can help Misplaced Pages by expanding it . Long range shooting There are several competitive match circuits that typically consist of targets at long range. Benchrest shooting events are often between 100 and 900 meters (≈ 100 to ≈ 1000 yards), F-Class

1674-451: Is most regularly held following the national championships in July each year. The first match, on Wednesday July 9, 1862, was held over 800 yd (730 m), 900 yd (820 m) and 1,000 yd (910 m) solely between Scotland and England. In the event England won by 166 points. Scotland won the trophy for the first time in 1864. As the match was restricted to Volunteers, Ireland

1736-422: Is scaled by a factor λ , should have the same statistical distribution as with β independent of the scale r . From this fact, and other results of Kolmogorov 1941 theory, it follows that the statistical moments of the flow velocity increments (known as structure functions in turbulence) should scale as where the brackets denote the statistical average, and the C n would be universal constants. There

1798-447: Is sufficiently high. Thus, Kolmogorov introduced a second hypothesis: for very high Reynolds numbers the statistics of small scales are universally and uniquely determined by the kinematic viscosity ν and the rate of energy dissipation ε . With only these two parameters, the unique length that can be formed by dimensional analysis is This is today known as the Kolmogorov length scale (see Kolmogorov microscales ). A turbulent flow

1860-401: Is the mean turbulent kinetic energy of the flow. The wavenumber k corresponding to length scale r is k = ⁠ 2π / r ⁠ . Therefore, by dimensional analysis, the only possible form for the energy spectrum function according with the third Kolmogorov's hypothesis is where K 0 ≈ 1.5 {\displaystyle K_{0}\approx 1.5} would be

1922-505: Is the velocity fluctuation, and τ {\displaystyle \tau } is the time lag between measurements. Although it is possible to find some particular solutions of the Navier–Stokes equations governing fluid motion, all such solutions are unstable to finite perturbations at large Reynolds numbers. Sensitive dependence on the initial and boundary conditions makes fluid flow irregular both in time and in space so that

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1984-522: Is to create realistic long range shooting competitions which are open to civilian sport shooters, police and military forces. A large emphasis is placed on safe firearm handling . Competitions can be held as either individual or two-person teamwork challenges. Competitions are divided into six major disciplines: Each target in every exercise is measured in milliradians (mrad) which takes into account its size and distance. There are also no-shoot targets which if struck incur penalties. The mrad system allows

2046-462: Is typically the same with 300 to 900 meters (≈ 300 to ≈ 1000 yards). A growing form of interdisciplinary shooting, becoming known as Practical Precision, places targets at virtually any distance from 100 to 1800 meters and the scoring is hit/ miss on steel targets of various sizes and from various positions (standing, kneeling, prone ). This type of match is quickly becoming more popular than F-Class. Few complete resources exist for teaching

2108-466: Is very small, which explain the success of Kolmogorov theory in regards to low order statistical moments. In particular, it can be shown that when the energy spectrum follows a power law with 1 < p < 3 , the second order structure function has also a power law, with the form Since the experimental values obtained for the second order structure function only deviate slightly from the ⁠ 2 / 3 ⁠ value predicted by Kolmogorov theory,

2170-404: The C n constants, are related with the phenomenon of intermittency in turbulence and can be related to the non-trivial scaling behavior of the dissipation rate averaged over scale r . This is an important area of research in this field, and a major goal of the modern theory of turbulence is to understand what is universal in the inertial range, and how to deduce intermittency properties from

2232-543: The NRA Imperial Meeting . The 2021 holder of the trophy is England. Each shooter fires fifteen shots at 1,000 yd (910 m), 1,100 yd (1,000 m), and 1,200 yd (1,100 m). Unusually, no "sighting" or practice shots are permitted. The shooters may be coached which allows other team members to judge and make necessary adjustments to the shooter's sights. The rules allow each team two hours at each distance to fire all their shots. The match

2294-523: The Reynolds number , which is the ratio of inertial forces to viscous forces within a fluid which is subject to relative internal movement due to different fluid velocities, in what is known as a boundary layer in the case of a bounding surface such as the interior of a pipe. A similar effect is created by the introduction of a stream of higher velocity fluid, such as the hot gases from a flame in air. This relative movement generates fluid friction, which

2356-640: The kinetic energy is significantly absorbed due to the action of fluid molecular viscosity gives rise to a laminar flow regime. For this the dimensionless quantity the Reynolds number ( Re ) is used as a guide. With respect to laminar and turbulent flow regimes: The Reynolds number is defined as where: While there is no theorem directly relating the non-dimensional Reynolds number to turbulence, flows at Reynolds numbers larger than 5000 are typically (but not necessarily) turbulent, while those at low Reynolds numbers usually remain laminar. In Poiseuille flow , for example, turbulence can first be sustained if

2418-493: The Reynolds number is larger than a critical value of about 2040; moreover, the turbulence is generally interspersed with laminar flow until a larger Reynolds number of about 4000. The transition occurs if the size of the object is gradually increased, or the viscosity of the fluid is decreased, or if the density of the fluid is increased. When flow is turbulent, particles exhibit additional transverse motion which enhances

2480-448: The art of shooting long ranges, but there are some dedicated resources and organizations with education as primary goal. The distances normally considered to be "long range" is weather- and caliber -dependent, and long range may be defined as stretching the distance at which the firearm and ammunition is capable of making consistent hits. Generally some may claim that for the .22 LR cartridge any distances over 100 metres (110 yd)

2542-576: The background. Ideally scope magnification should be high enough while still being comfortable and safe to use. Pros of high scope magnification are: Cons of high scope magnification are: Mirage is a light distortion caused by temperature differences between the air and ground making it difficult to get a clear sight picture of the target. Mirage becomes more apparent the higher the magnification, but at what magnification mirage starts to become an issue depends on weather conditions. Turbulence In fluid dynamics , turbulence or turbulent flow

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2604-492: The dimensionless Reynolds number , the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence create a very complex phenomenon. Physicist Richard Feynman described turbulence as the most important unsolved problem in classical physics. The turbulence intensity affects many fields, for examples fish ecology, air pollution, precipitation, and climate change. Turbulence

2666-422: The effect they pose is so small that they generally can be disregarded. At short distances the accuracy of the shooter, rifle and ammunition will often mask the very small effect these factors will have. For long range shooting it is important to compensate for the wind by observing the wind's strength and direction, and then adjust the sights accordingly by rules of thumb . Wind force can be estimated by feeling

2728-581: The first." A similar witticism has been attributed to Horace Lamb in a speech to the British Association for the Advancement of Science : "I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather more optimistic." The onset of turbulence can be, to some extent, predicted by

2790-499: The fluid, μ turb is the coefficient of turbulent viscosity and k turb is the turbulent thermal conductivity . Richardson's notion of turbulence was that a turbulent flow is composed by "eddies" of different sizes. The sizes define a characteristic length scale for the eddies, which are also characterized by flow velocity scales and time scales (turnover time) dependent on the length scale. The large eddies are unstable and eventually break up originating smaller eddies, and

2852-399: The kinetic energy of the initial large eddy is divided into the smaller eddies that stemmed from it. These smaller eddies undergo the same process, giving rise to even smaller eddies which inherit the energy of their predecessor eddy, and so on. In this way, the energy is passed down from the large scales of the motion to smaller scales until reaching a sufficiently small length scale such that

2914-454: The magnification somewhat (i.e. to 10× magnification). To succeed at long range shooting, one must have good shooting skill fundamentals, a rifle with good precision and as consistent ammunition as possible (mainly to achieve a consistent muzzle velocity ). In addition, a variety of external factors must be taken into account with regard to ballistics calculation, including: etc. All these parameters can also be used at shorter distances, but

2976-546: The marksman must also judge the distances, for example by comparing a known size target with angular mil hashmarks inside their scope (called "milling") to calculate the distance. Sometimes a laser rangefinder may also be used, if permitted. T-Class shooting , founded in 2014, is a sport mainly focused on competitions with precision rifle systems for various short, medium and long range distances, which may either be known or unknown. Headquarters reside in Bulgaria, and for

3038-513: The module's stages. The competitor with highest summarized result is awarded with 100 percent. The scoring for the other competitors is made proportionally in relation to the highest summarized score, with calculation up to two decimal places. The calculated sum in percentage from all the three Modules assembles the Match ranking and demonstrates the winner. Precision rifle competition is a relatively new long-range competition format which seeks to find

3100-498: The onset of turbulent flow is an important design tool for equipment such as piping systems or aircraft wings, but the Reynolds number is also used in scaling of fluid dynamics problems, and is used to determine dynamic similitude between two different cases of fluid flow, such as between a model aircraft, and its full size version. Such scaling is not always linear and the application of Reynolds numbers to both situations allows scaling factors to be developed. A flow situation in which

3162-460: The particular geometrical features of the boundaries (the size characterizing the large scales will be denoted as L ). Kolmogorov's idea was that in the Richardson's energy cascade this geometrical and directional information is lost, while the scale is reduced, so that the statistics of the small scales has a universal character: they are the same for all turbulent flows when the Reynolds number

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3224-408: The phenomenon. The main cause is probably contrails which appear around the bullet due to pressure changes as the bullet travels through the air, thereby causing a short change in the light refraction of the air. In order for the shooter to see their own bullet trace, the bullet trajectory must be within the field of view of their scope sight. In practice this often means the shooter has to dial down

3286-444: The purpose of promotion of the sport internationally the organization offers a ruleset which regulates the design and management of competitions. Competitions consist of several stages, and the competitors have to move between different parts of the stage under a time limitation, quickly assume stable or unstable shooting positions, and use theoretical background to successfully make precise long range shots. The main idea behind T-Class

3348-421: The rate of energy and momentum exchange between them thus increasing the heat transfer and the friction coefficient. Assume for a two-dimensional turbulent flow that one was able to locate a specific point in the fluid and measure the actual flow velocity v = ( v x , v y ) of every particle that passed through that point at any given time. Then one would find the actual flow velocity fluctuating about

3410-586: The reference frame) this is usually done by means of the energy spectrum function E ( k ) , where k is the modulus of the wavevector corresponding to some harmonics in a Fourier representation of the flow velocity field u ( x ) : where û ( k ) is the Fourier transform of the flow velocity field. Thus, E ( k ) d k represents the contribution to the kinetic energy from all the Fourier modes with k < | k | < k + d k , and therefore, where ⁠ 1 / 2 ⁠ ⟨ u i u i ⟩

3472-526: The shooter has a time limit to move between the various courses of fire. Each course usually has a set maximum time (par time), and the shooter is awarded points according to how many targets he manages to hit during that time. Both cardboard and steel targets are used, and the targets presented are usually relatively small. In the PRS-series for instance, the targets are usually between 0.3-0.9 MIL (3–9 cm at 100 m, approximately 1-3 MOA ). F-Class

3534-400: The statistical description is presently modified. A complete description of turbulence is one of the unsolved problems in physics . According to an apocryphal story, Werner Heisenberg was asked what he would ask God , given the opportunity. His reply was: "When I meet God, I am going to ask him two questions: Why relativity ? And why turbulence? I really believe he will have an answer for

3596-431: The usage of virtually all kinds of shooting targets , like paper, steel or clay targets, golf balls , soda cans , etc. Scoring is made with points attributed to the angular measurements of the target according to pre-defined tables. For some stages of Module 2 and 3, the so-called hit factor is applied (the score on the targets divided by the time used on that stage). The scoring is calculated by adding results from all

3658-403: The value for p is very near to ⁠ 5 / 3 ⁠ (differences are about 2% ). Thus the "Kolmogorov − ⁠ 5 / 3 ⁠ spectrum" is generally observed in turbulence. However, for high order structure functions, the difference with the Kolmogorov scaling is significant, and the breakdown of the statistical self-similarity is clear. This behavior, and the lack of universality of

3720-400: The viscosity of the fluid can effectively dissipate the kinetic energy into internal energy. In his original theory of 1941, Kolmogorov postulated that for very high Reynolds numbers , the small-scale turbulent motions are statistically isotropic (i.e. no preferential spatial direction could be discerned). In general, the large scales of a flow are not isotropic, since they are determined by

3782-585: The wind at the shooting position and seeing signs of it in the terrain. For instance, after guessing the wind strength in meters per second (m/s), this wind value can be transferred to a sight correction in number of clicks. This rule of thumb applies to winds that come 90 degree from the side (full value), however winds coming from an angle must be taken into account by applying less sight adjustment. There are many different long range disciplines, competing both at known (KD) and unknown distances (UKD), individually or in teams (shooter and spotter). In UKD competitions

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3844-681: Was unable to participate - having no Volunteer regiments. After several applications, the NRA permitted the Ulster Rifle Association to send a team and Ireland joined the fray in 1865. Ireland scored their first win in 1873. By this time, the match had become a major sporting event in Victorian England, as important as The Boat Race or the Eton v Harrow cricket match at Lords. Wales did not compete until 1991. The Elcho Shield

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