tax query by id
$tax_query = array( 'relation' => 'OR', array( 'taxonomy' => 'product_category', 'terms' => array( '1', '2', '3' ), 'field' => 'term_id', ), );
$tax_query = array( 'relation' => 'OR', array( 'taxonomy' => 'product_category', 'terms' => array( '1', '2', '3' ), 'field' => 'term_id', ), );