<<< native
[ ESymbol Ord "\8711"
, ESymbol Bin "\8901"
, EOver False (EIdentifier "v") (ESymbol Accent "\8407")
, ESymbol Rel "="
, EFraction
    NormalFrac
    (EGrouped
       [ ESymbol Ord "\8706" , ESub (EIdentifier "v") (EIdentifier "x") ])
    (EGrouped [ ESymbol Ord "\8706" , EIdentifier "x" ])
, ESymbol Bin "+"
, EFraction
    NormalFrac
    (EGrouped
       [ ESymbol Ord "\8706" , ESub (EIdentifier "v") (EIdentifier "y") ])
    (EGrouped [ ESymbol Ord "\8706" , EIdentifier "y" ])
, ESymbol Bin "+"
, EFraction
    NormalFrac
    (EGrouped
       [ ESymbol Ord "\8706" , ESub (EIdentifier "v") (EIdentifier "z") ])
    (EGrouped [ ESymbol Ord "\8706" , EIdentifier "z" ])
]
>>> omml
<?xml version='1.0' ?>
<m:oMathPara>
  <m:oMathParaPr>
    <m:jc m:val="center" />
  </m:oMathParaPr>
  <m:oMath>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>∇</m:t>
    </m:r>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>⋅</m:t>
    </m:r>
    <m:acc>
      <m:accPr>
        <m:chr m:val="⃗" />
      </m:accPr>
      <m:e>
        <m:r>
          <m:t>v</m:t>
        </m:r>
      </m:e>
    </m:acc>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>=</m:t>
    </m:r>
    <m:f>
      <m:fPr>
        <m:type m:val="bar" />
      </m:fPr>
      <m:num>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:sSub>
          <m:e>
            <m:r>
              <m:t>v</m:t>
            </m:r>
          </m:e>
          <m:sub>
            <m:r>
              <m:t>x</m:t>
            </m:r>
          </m:sub>
        </m:sSub>
      </m:num>
      <m:den>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:r>
          <m:t>x</m:t>
        </m:r>
      </m:den>
    </m:f>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>+</m:t>
    </m:r>
    <m:f>
      <m:fPr>
        <m:type m:val="bar" />
      </m:fPr>
      <m:num>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:sSub>
          <m:e>
            <m:r>
              <m:t>v</m:t>
            </m:r>
          </m:e>
          <m:sub>
            <m:r>
              <m:t>y</m:t>
            </m:r>
          </m:sub>
        </m:sSub>
      </m:num>
      <m:den>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:r>
          <m:t>y</m:t>
        </m:r>
      </m:den>
    </m:f>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>+</m:t>
    </m:r>
    <m:f>
      <m:fPr>
        <m:type m:val="bar" />
      </m:fPr>
      <m:num>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:sSub>
          <m:e>
            <m:r>
              <m:t>v</m:t>
            </m:r>
          </m:e>
          <m:sub>
            <m:r>
              <m:t>z</m:t>
            </m:r>
          </m:sub>
        </m:sSub>
      </m:num>
      <m:den>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∂</m:t>
        </m:r>
        <m:r>
          <m:t>z</m:t>
        </m:r>
      </m:den>
    </m:f>
  </m:oMath>
</m:oMathPara>